Extract Uploader's Avatar on YouTube and PeerTube

[FireMasterK]

• I carefully read the contribution guidelines and agree to them.
• I have tested the API against NewPipe.
• I agree to create a pull request for NewPipe as soon as possible to make it compatible with the changed API.

This pull request adds support for Channel Avatars extraction in the StreamInfoItem class.

[Stypox]

Thank you @FireMasterK! Could you add some description? Does this add support for channel avatars of stream info items?

[FireMasterK]

Thank you @FireMasterK! Could you add some description? Does this add support for channel avatars of stream info items?

Done! It indeed does, this currently only works in the Search and Trending pages I believe as YouTube doesn't provide these anywhere else.

[Stypox]

Looks almost good to me :-)

[TobiGr]

I think this can also be tested roughly in DefaultTests.defaultTestListOfItems().

Please remove throws ParsingException when overriding the method and returning null

[FireMasterK]

I think this can also be tested roughly in DefaultTests.defaultTestListOfItems().

What about services which in which it's not extracted in? Another thing to note is that even on YouTube, it's not provided everywhere.

[TobiGr]

Testing this should be similar to testing the thumbnail URL

            final String uploaderAvatarUrl = item.getUploaderAvatarUrl();
            if (!isNullOrEmpty(uploaderAvatarUrl)) {
                assertIsSecureUrl(uploaderAvatarUrl);
            }

[FireMasterK]

Testing this should be similar to testing the thumbnail URL

            final String uploaderAvatarUrl = item.getUploaderAvatarUrl();
            if (!isNullOrEmpty(uploaderAvatarUrl)) {
                assertIsSecureUrl(uploaderAvatarUrl);
            }

Added, thanks for the clarification on what you meant!