Extract visitor data from YouTube API

[Ales315]

This fix is based on the code of this PR again from TeamNewPipe TeamNewPipe/NewPipeExtractor#1271
A bit rough cosmetically-wise but it's the best I could do 😀

Note that if the structure of the json changes this solution can fail as the extraction logic is hardcoded.

Closes #868

[Jacobwasbeast]

I can confirm, it did fix the 'sign in' error on my app.

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YoutubeExplode/Bridge/VisitorData.cs:86

• The error message 'Failed to fetch visitor data' is unclear. It should include more context about the failure, such as the URL or response status.

throw new Exception("Failed to fetch visitor data");

YoutubeExplode/Bridge/VisitorData.cs:44

• The new behavior introduced by the function 'ExtractFromYoutube' should be covered by tests to ensure it works as expected.

public static async Task<string> ExtractFromYoutube(HttpClient http)