feat: add ChannelRss

- add documentation
- small model refactor: rename player VideoPlayerDetails.thumbnails to thumbnail

testfiles/player_model/hdr.json

@@ -4,7 +4,7 @@
     "title": "COSTA RICA IN 4K 60fps HDR (ULTRA HD)",
     "description": "We've re-mastered and re-uploaded our favorite video in HDR!\n\nCHECK OUT OUR MOST POPULAR VIDEO: https://youtu.be/tO01J-M3g0U\n► INSTAGRAM: http://www.instagram.com/mysterybox\n► INSTAGRAM: http://www.instagram.com/jacobschwarz\n►WEBSITE: http://www.mysterybox.us\n►FACEBOOK: https://www.facebook.com/mysteryboxdi...\n\nMake sure to follow us on Instagram for BTS and sneak-peaks at upcoming projects. \n\nLICENSING & BUSINESS INQUIRIES\n► contact@mysterybox.us\n\nCHECK OUT OUR VIDEO PRODUCTION COMPANY\n► https://www.mysterybox.us\n\n4K PLAYLISTS\n► https://www.youtube.com/playlist?list...\n\nBLOG Check out our blog for great information on working in HDR and 8K. \n► http://www.mysterybox.us/blog\n\nSUBSCRIBE FOR MORE VIDS\n►https://www.youtube.com/user/jacobsch...\n\nMUSIC\n► Storyworks Music \"Promise of Dawn\"\nhttps://soundcloud.com/joshuapeterson/promise-of-dawn\nwww.storyworksmusic.com\n\n► SHOT ON\nRed Weapon LE w/Helium 8K s35 sensor (Stormtrooper33)\nCanon 16-35mm III  \nCanon 24-70mm II\nSigma 150-500mm\nZeiss Classic 15mm\nMOVI M10\nAdobe Premiere and DaVinci Resolve\n\n\n\nLICENSING & BUSINESS INQUIRIES\n► contact@mysterybox.us\n\nThis video is subject to copyright owned by Mystery Box LLC. Any reproduction or republication of all or part of this video is expressly prohibited, unless Mystery Box has explicitly granted its prior written consent. All other rights reserved.\n\nCopyright © 2017 Mystery Box, LLC. All Rights Reserved.",
     "length": 314,
-    "thumbnails": [
+    "thumbnail": [
       {
         "url": "https://i.ytimg.com/vi/LXb3EKWsInQ/hqdefault.jpg?sqp=-oaymwEbCKgBEF5IVfKriqkDDggBFQAAiEIYAXABwAEG&rs=AOn4CLC0YPk1n3EyXOsJxvBcJsAgR1umog",
         "width": 168,