add HDR Support

Although tunneled playback is enabled on the player in the client, without proper extractor support, HDR will not work.

Here's a snippet from youtube-dl, as you can see, all HDR content has Itag of 33x:

youtube-dl.exe -F https://www.youtube.com/watch?v=WW2DKBGCvEs
[youtube] WW2DKBGCvEs: Downloading webpage
[youtube] WW2DKBGCvEs: Downloading video info webpage
[youtube] WW2DKBGCvEs: Extracting video information
[youtube] WW2DKBGCvEs: Downloading MPD manifest
[info] Available formats for WW2DKBGCvEs:
format code extension resolution note
139 m4a audio only DASH audio 48k , m4a_dash container, mp4a.40.5@ 48k (22050Hz), 683.89KiB
249 webm audio only DASH audio 55k , opus @ 50k, 771.41KiB
250 webm audio only DASH audio 80k , opus @ 70k, 1.07MiB
140 m4a audio only DASH audio 127k , m4a_dash container, mp4a.40.2@128k (44100Hz), 1.78MiB
171 webm audio only DASH audio 132k , vorbis@128k, 1.73MiB
251 webm audio only DASH audio 151k , opus @160k, 2.03MiB
160 mp4 256x144 DASH video 47k , avc1.4d400c, 24fps, video only, 470.93KiB
278 webm 256x144 144p 97k , webm container, vp9, 24fps, video only, 1.24MiB
330 webm 256x144 144p HDR 147k , vp9.2, 24fps, video only, 1.73MiB
242 webm 426x240 240p 173k , vp9, 24fps, video only, 1.82MiB
133 mp4 426x240 DASH video 182k , avc1.4d4015, 24fps, video only, 1.83MiB
331 webm 426x240 240p HDR 241k , vp9.2, 24fps, video only, 2.96MiB
134 mp4 640x360 DASH video 280k , avc1.4d401e, 24fps, video only, 2.81MiB
243 webm 640x360 360p 364k , vp9, 24fps, video only, 3.96MiB
332 webm 640x360 360p HDR 457k , vp9.2, 24fps, video only, 5.80MiB
135 mp4 854x480 DASH video 631k , avc1.4d401e, 24fps, video only, 6.27MiB
244 webm 854x480 480p 662k , vp9, 24fps, video only, 7.10MiB
333 webm 854x480 480p HDR 864k , vp9.2, 24fps, video only, 10.99MiB
136 mp4 1280x720 DASH video 1319k , avc1.4d401f, 24fps, video only, 13.16MiB
247 webm 1280x720 720p 1466k , vp9, 24fps, video only, 16.15MiB
334 webm 1280x720 720p HDR 1821k , vp9.2, 24fps, video only, 22.38MiB
248 webm 1920x1080 1080p 2723k , vp9, 24fps, video only, 32.02MiB
137 mp4 1920x1080 DASH video 2875k , avc1.640028, 24fps, video only, 28.16MiB
335 webm 1920x1080 1080p HDR 3181k , vp9.2, 24fps, video only, 40.02MiB
271 webm 2560x1440 1440p 7477k , vp9, 24fps, video only, 86.30MiB
264 mp4 2560x1440 DASH video 7973k , avc1.640032, 24fps, video only, 79.24MiB
336 webm 2560x1440 1440p HDR 11586k , vp9.2, 24fps, video only, 143.43MiB
337 webm 3840x2160 2160p HDR 19690k , vp9.2, 24fps, video only, 260.42MiB
266 mp4 3840x2160 DASH video 21183k , avc1.640033, 24fps, video only, 218.04MiB
313 webm 3840x2160 2160p 21927k , vp9, 24fps, video only, 245.45MiB
17 3gp 176x144 small , mp4v.20.3, mp4a.40.2@ 24k
36 3gp 320x180 small , mp4v.20.3, mp4a.40.2
43 webm 640x360 medium , vp8.0, vorbis@128k
18 mp4 640x360 medium , avc1.42001E, mp4a.40.2@ 96k
22 mp4 1280x720 hd720 , avc1.64001F, mp4a.40.2@192k (best)

No file or test is named. Start by tracing the extractor's handling of YouTube video formats and the HDR itags in the issue, then determine where those formats are filtered or represented. Done means HDR formats are recognized and exposed for playback, with coverage for the listed HDR itags.