feat(Author): Add collaborators field

[Shadorc]

Add Collaborator class and add support for collaborators field inside Author.

This adds support for collaborators in search page data.
This does not work for in channel (example) or playlist (example) because YouTube does not provide this data.
Video page does not use Author class for parsing and rely on LockupView.

Playlists themselves can also be collaborative, but it does not seem to be supported by YouTube's API. The response from Innertube (Innertube#getPlaylist) does not contain any mention to collaborators other than their thumbnails.
Example: https://www.youtube.com/playlist?list=PLaen7aJT3lIFptMwtTJkOvQtcxyKqQwlP

Tested in FreeTube.

Example for a author.collaborators field in search results:

[
    {
        "id": "UCGmnsW623G1r-Chmo5RB4Yw",
        "name": "KSI",
        "thumbnails": [
            {
                "url": "https://yt3.ggpht.com/2f8wOz76TImPcmiuUYSgJQbQnjEKXlD01_kw284BOI_DrQS4tYS6Q97DMW-yffRT-pVYIs6a=s68-c-k-c0x00ffffff-no-rj"
            }
        ],
        "url": "https://www.youtube.com/channel/UCGmnsW623G1r-Chmo5RB4Yw",
        "channel_info": "‎⁨@KSI⁩ • ⁨18.4M subscribers⁩"
    },
    {
        "id": "UCfNWN9s_s8kRTCadk04WWJA",
        "name": "TBJZL",
        "thumbnails": [
            {
                "url": "https://yt3.ggpht.com/ytc/AIdro_miigxDW5yfl6sZ3g0VgJjUKb-VwkeCabLQHxxSgFKaLw=s88-c-k-c0x00ffffff-no-rj"
            }
        ],
        "url": "https://www.youtube.com/channel/UCfNWN9s_s8kRTCadk04WWJA",
        "channel_info": "‎⁨@TBJZL⁩ • ⁨5.13M subscribers⁩"
    },
    {
        "id": "UC1crUC35Gk-U_-rv5sM4PtA",
        "name": "Manny",
        "thumbnails": [
            {
                "url": "https://yt3.ggpht.com/NtkemzY0BCz7WDjNtKKNBz9IOELHjxuH82HOM8uAC148y_k4Sd_sbrqmIanteyCdDihEhGFp-g=s88-c-k-c0x00ffffff-no-rj"
            }
        ],
        "url": "https://www.youtube.com/channel/UC1crUC35Gk-U_-rv5sM4PtA",
        "channel_info": "‎⁨@Manny⁩ • ⁨2.15M subscribers⁩"
    }
]