mpv: Use yt-dlp instead of youtube-dl

Switch to fork since it's more actively developed and contains some
additional features. Primarily switched since it had quite a bit better
subtitle stream handling than the original for quite a while.

mpv/.config/mpv/script-opts/ytdl_hook.conf

@@ -0,0 +1,2 @@
+# use fork instead
+ytdl_path=yt-dlp

nvim/.config/nvim/spell/en.utf-8.add

@@ -175,3 +175,4 @@ triadic
 neoliberalism's
 ascriptions
 exploitations
+tradeable