[Bug] Mix playlists render as -1 videos

[Fijxu]

Playlists cataloged as a Mix (which are playlists generated by Youtube) have a video count of -1 video. It should display Mix instead of the quantity of videos the playlist has.

Lines that need to be fixed:

https://github.com/iv-org/invidious/blob/89c8b1b901062c729370370116aa9127a39cd214/src/invidious/yt_backend/extractors.cr#L673-L679

JSON looks like this:

"thumbnailOverlayBadgeViewModel": {
	"thumbnailBadges": [
		{
			"thumbnailBadgeViewModel": {
				"icon": {
					"sources": [
						{
							"clientResource": {
								"imageName": "MIX"
							}
						}
					]
				},
				"text": "Mix", # THIS LINE NEEDS TO BE CONSIDERED
				"badgeStyle": "THUMBNAIL_OVERLAY_BADGE_STYLE_DEFAULT"
			}
		}
	],
	"position": "THUMBNAIL_OVERLAY_BADGE_POSITION_BOTTOM_END"
}