Feature Request: Support for bundle tree on AssetsManifest

[danielbarion]

Description

Hey guys, first of all, thank you so much for this project, I'm following on Discord and the community is very proactive and helpful, great job, v8 looks like an amazing improvement, I'll update my pet project to v8 after I finish some things I'm learning.

I was checking the AssetsManifest typescript attributes, and as far as I understand, today it is not possible to have a tree of assets on AssetsManifest (tests).

So, today I'm splitting it into a few files, but I'm parsing them in the end to reach the right approach that Pixijs expects

It would be nice to have the possibility to do something like this:

[
  {
      "name": "login",
      "assets": [
          {
              "name": "login_background",
              "srcs": "http://localhost:3000/assets/login_background.jpeg"
          },
          {
              "name": "login_input_normal",
              "srcs": "http://localhost:3000/assets/input_normal.png"
          }
      ]
  },
  {
      "name": "items",
      "tree": [      // "tree" is just an example, I didn't think in a better name while writing this
    {
        "name": "weapons",
        "assets": [
            {
                "name": "sword",
                "srcs": "http://localhost:3000/assets/items/weapons/Icon_Sword_128.png"
            }
        ]
    },
    {
        "name": "books",
        "assets": [
            {
                "name": "book_1",
                "srcs": "http://localhost:3000/assets/items/books/1.png"
            },
            {
                "name": "book_2",
                "srcs": "http://localhost:3000/assets/items/books/2.png"
            },
            {
                "name": "book_3",
                "srcs": "http://localhost:3000/assets/items/books/3.png"
            }
        ]
    }
   ]
  },
]

Instead of:

[
  {
      "name": "login",
      "assets": [
          {
              "name": "login_background",
              "srcs": "http://localhost:3000/assets/login_background.jpeg"
          },
          {
              "name": "login_input_normal",
              "srcs": "http://localhost:3000/assets/input_normal.png"
          }
      ]
  },
    {
        "name": "weapons",
        "assets": [
            {
                "name": "sword",
                "srcs": "http://localhost:3000/assets/items/weapons/Icon_Sword_128.png"
            }
        ]
    },
    {
        "name": "books",
        "assets": [
            {
                "name": "book_1",
                "srcs": "http://localhost:3000/assets/items/books/1.png"
            },
            {
                "name": "book_2",
                "srcs": "http://localhost:3000/assets/items/books/2.png"
            },
            {
                "name": "book_3",
                "srcs": "http://localhost:3000/assets/items/books/3.png"
            }
        ]
    }
]

It would be nice to have more flexibility on how we can organize the assets manifest data.