feat: add support for /show/ urls

src/invidious/routes/playlists.cr

@@ -387,6 +387,7 @@ module Invidious::Routes::Playlists
     referer = get_referer(env)
 
     plid = env.params.query["list"]?.try &.gsub(/[^a-zA-Z0-9_-]/, "")
+    plid ||= env.params.url["id"]?.try &.[2..]
     if !plid
       return env.redirect "/"
     end

src/invidious/routing.cr

@@ -178,6 +178,7 @@ module Invidious::Routing
 
   def register_yt_playlist_routes
     get "/playlist", Routes::Playlists, :show
+    get "/show/:id", Routes::Playlists, :show
     get "/mix", Routes::Playlists, :mix
     get "/watch_videos", Routes::Playlists, :watch_videos
   end