API: Parse multiimage community posts

[ChunkyProgrammer]

#3522
FreeTubeApp/FreeTube#1568

This PR will allow the parsing of "MultiImage" community posts. It's essentially an array of image thumbnails.
This is an example of how the attachment is formatted:

      "attachment": {
        "type": "multiImage",
        "images": [
          [
            {
              "url": "https://yt3.ggpht.com/lveyJ9xgshW-HMEXABj2qpVWE3tfpxmxGWUaJxoyFOirBDkOiAy1gQnWfsS0mrTasGcIo6akAv9E__U=s320-c-fcrop64=1,000029fcfffff6c8-nd-v1",
              "width": 320,
              "height": 320
            },
            {
              "url": "https://yt3.ggpht.com/lveyJ9xgshW-HMEXABj2qpVWE3tfpxmxGWUaJxoyFOirBDkOiAy1gQnWfsS0mrTasGcIo6akAv9E__U=s560-c-fcrop64=1,000029fcfffff6c8-nd-v1",
              "width": 560,
              "height": 560
            },
            {
              "url": "https://yt3.ggpht.com/lveyJ9xgshW-HMEXABj2qpVWE3tfpxmxGWUaJxoyFOirBDkOiAy1gQnWfsS0mrTasGcIo6akAv9E__U=s640-c-fcrop64=1,000029fcfffff6c8-nd-v1",
              "width": 640,
              "height": 640
            },
            {
              "url": "https://yt3.ggpht.com/lveyJ9xgshW-HMEXABj2qpVWE3tfpxmxGWUaJxoyFOirBDkOiAy1gQnWfsS0mrTasGcIo6akAv9E__U=s1280-c-fcrop64=1,000029fcfffff6c8-nd-v1",
              "width": 1280,
              "height": 1280
            },
            {
              "url": "https://yt3.ggpht.com/lveyJ9xgshW-HMEXABj2qpVWE3tfpxmxGWUaJxoyFOirBDkOiAy1gQnWfsS0mrTasGcIo6akAv9E__U=s2000-c-fcrop64=1,000029fcfffff6c8-nd-v1",
              "width": 2000,
              "height": 2000
            }
          ],
          [
            {
              "url": "https://yt3.ggpht.com/1Y1FPvZeQ7B-AuRy2umFkMimXHu6ifJCKRtkLG6NOUFnm2tRaoMBnRyoGzQ7y2GUIsnrRiC5uUsyDg=s320-c-fcrop64=1,00000000ffffffff-nd-v1",
              "width": 320,
              "height": 320
            },
            {
              "url": "https://yt3.ggpht.com/1Y1FPvZeQ7B-AuRy2umFkMimXHu6ifJCKRtkLG6NOUFnm2tRaoMBnRyoGzQ7y2GUIsnrRiC5uUsyDg=s560-c-fcrop64=1,00000000ffffffff-nd-v1",
              "width": 560,
              "height": 560
            },
            {
              "url": "https://yt3.ggpht.com/1Y1FPvZeQ7B-AuRy2umFkMimXHu6ifJCKRtkLG6NOUFnm2tRaoMBnRyoGzQ7y2GUIsnrRiC5uUsyDg=s640-c-fcrop64=1,00000000ffffffff-nd-v1",
              "width": 640,
              "height": 640
            },
            {
              "url": "https://yt3.ggpht.com/1Y1FPvZeQ7B-AuRy2umFkMimXHu6ifJCKRtkLG6NOUFnm2tRaoMBnRyoGzQ7y2GUIsnrRiC5uUsyDg=s1280-c-fcrop64=1,00000000ffffffff-nd-v1",
              "width": 1280,
              "height": 1280
            },
            {
              "url": "https://yt3.ggpht.com/1Y1FPvZeQ7B-AuRy2umFkMimXHu6ifJCKRtkLG6NOUFnm2tRaoMBnRyoGzQ7y2GUIsnrRiC5uUsyDg=s2000-c-fcrop64=1,00000000ffffffff-nd-v1",
              "width": 2000,
              "height": 2000
            }
          ],
          [
            {
              "url": "https://yt3.ggpht.com/glqnpJulKWdDr_L6BfTXX8g0HrdCDx4AhsA2WkNnRTSLPpj_MIiP7K52a9-kX4SWCLd-grH4Si5Jdnw=s320-c-fcrop64=1,008c0000ff73ffff-nd-v1",
              "width": 320,
              "height": 320
            },
            {
              "url": "https://yt3.ggpht.com/glqnpJulKWdDr_L6BfTXX8g0HrdCDx4AhsA2WkNnRTSLPpj_MIiP7K52a9-kX4SWCLd-grH4Si5Jdnw=s560-c-fcrop64=1,008c0000ff73ffff-nd-v1",
              "width": 560,
              "height": 560
            },
            {
              "url": "https://yt3.ggpht.com/glqnpJulKWdDr_L6BfTXX8g0HrdCDx4AhsA2WkNnRTSLPpj_MIiP7K52a9-kX4SWCLd-grH4Si5Jdnw=s640-c-fcrop64=1,008c0000ff73ffff-nd-v1",
              "width": 640,
              "height": 640
            },
            {
              "url": "https://yt3.ggpht.com/glqnpJulKWdDr_L6BfTXX8g0HrdCDx4AhsA2WkNnRTSLPpj_MIiP7K52a9-kX4SWCLd-grH4Si5Jdnw=s1280-c-fcrop64=1,008c0000ff73ffff-nd-v1",
              "width": 1280,
              "height": 1280
            },
            {
              "url": "https://yt3.ggpht.com/glqnpJulKWdDr_L6BfTXX8g0HrdCDx4AhsA2WkNnRTSLPpj_MIiP7K52a9-kX4SWCLd-grH4Si5Jdnw=s2000-c-fcrop64=1,008c0000ff73ffff-nd-v1",
              "width": 2000,
              "height": 2000
            }
          ],
          [
            {
              "url": "https://yt3.ggpht.com/TI7Hl13GxRZz406yEWfdsdoM0_AIuuTqM8ZQ4b8kUdjFT92xzW3WvP_HIQ0Dutf1DXqfOsh4UShwZAQ=s320-c-fcrop64=1,0bec0000b69fffff-nd-v1",
              "width": 320,
              "height": 320
            },
            {
              "url": "https://yt3.ggpht.com/TI7Hl13GxRZz406yEWfdsdoM0_AIuuTqM8ZQ4b8kUdjFT92xzW3WvP_HIQ0Dutf1DXqfOsh4UShwZAQ=s560-c-fcrop64=1,0bec0000b69fffff-nd-v1",
              "width": 560,
              "height": 560
            },
            {
              "url": "https://yt3.ggpht.com/TI7Hl13GxRZz406yEWfdsdoM0_AIuuTqM8ZQ4b8kUdjFT92xzW3WvP_HIQ0Dutf1DXqfOsh4UShwZAQ=s640-c-fcrop64=1,0bec0000b69fffff-nd-v1",
              "width": 640,
              "height": 640
            },
            {
              "url": "https://yt3.ggpht.com/TI7Hl13GxRZz406yEWfdsdoM0_AIuuTqM8ZQ4b8kUdjFT92xzW3WvP_HIQ0Dutf1DXqfOsh4UShwZAQ=s1280-c-fcrop64=1,0bec0000b69fffff-nd-v1",
              "width": 1280,
              "height": 1280
            },
            {
              "url": "https://yt3.ggpht.com/TI7Hl13GxRZz406yEWfdsdoM0_AIuuTqM8ZQ4b8kUdjFT92xzW3WvP_HIQ0Dutf1DXqfOsh4UShwZAQ=s2000-c-fcrop64=1,0bec0000b69fffff-nd-v1",
              "width": 2000,
              "height": 2000
            }
          ],
          [
            {
              "url": "https://yt3.ggpht.com/pCRgvqzJPeW1mXhNSTW9_Ukvzn4z0UFZN9BgG6M96A_UIMx2D9Ko5EQcm6HaN52urORrZhX25gMHCQ=s320-c-fcrop64=1,1eb30000c966ffff-nd-v1",
              "width": 320,
              "height": 320
            },
            {
              "url": "https://yt3.ggpht.com/pCRgvqzJPeW1mXhNSTW9_Ukvzn4z0UFZN9BgG6M96A_UIMx2D9Ko5EQcm6HaN52urORrZhX25gMHCQ=s560-c-fcrop64=1,1eb30000c966ffff-nd-v1",
              "width": 560,
              "height": 560
            },
            {
              "url": "https://yt3.ggpht.com/pCRgvqzJPeW1mXhNSTW9_Ukvzn4z0UFZN9BgG6M96A_UIMx2D9Ko5EQcm6HaN52urORrZhX25gMHCQ=s640-c-fcrop64=1,1eb30000c966ffff-nd-v1",
              "width": 640,
              "height": 640
            },
            {
              "url": "https://yt3.ggpht.com/pCRgvqzJPeW1mXhNSTW9_Ukvzn4z0UFZN9BgG6M96A_UIMx2D9Ko5EQcm6HaN52urORrZhX25gMHCQ=s1280-c-fcrop64=1,1eb30000c966ffff-nd-v1",
              "width": 1280,
              "height": 1280
            },
            {
              "url": "https://yt3.ggpht.com/pCRgvqzJPeW1mXhNSTW9_Ukvzn4z0UFZN9BgG6M96A_UIMx2D9Ko5EQcm6HaN52urORrZhX25gMHCQ=s2000-c-fcrop64=1,1eb30000c966ffff-nd-v1",
              "width": 2000,
              "height": 2000
            }
          ]
        ]
      }

I do not plan on adding support for viewing these posts in invidious at this time as I am unfamiliar with ecr files and I think adding support may require a js library or doing something like this (which is not keyboard accessible): https://medium.com/carwow-product-engineering/making-a-carousel-component-without-javascript-f7c68e3e6f8b

Another option would be to have a div with a scrollbar to allow scrolling to different images.

[SamantazFox]

Thanks for your contribution ^^