Bump version to v2.1.2

Bump version to v2.1.1, and refine comments

Fix automatic secondary subtitles selection

Bump version to v2.0.1

Update README.md and README_en.md

Remove `hobodrifterdavid` from the maintainers, as he clearly
does not actively keep this extension working/updated.

Bump version to v1.6.7

Fix the manifest ID checking (#20)

Recently we discover some Netflix episodes can likely have multiple URLs (i.e.
different manifest ID in the `netflix.com/watch/12345678` URL format).

This breaks our checking of manifest ID (refer to #5).  Thus when the loaded
manifest ID does not present in URL, we check the player's DOM tree as an
alternative way... tricky but works (at least for now).

Fix overlap (z-index) issue for new player UI (#19)

After some users being upgraded to a version of web player with fancy controls
(codename: `Neo`), users' clicks on the control buttons are not effective
because we don't adjust the z-index of Neo controls.

Bump version to v1.6.4 🎊

Fix: ignore preloaded manifest (not playing) (#5)