Russian translation

• Added Russian translation, thanks to @dexianox !

Ukrainian translation

• Added Ukrainian translation, thanks to @S-te-Fan!

Turkish translation

• Added Turkish translation, thanks to @Sibernatif!

Chinese translation

• Added Chinese translation, thanks to @ClewenWei!

Czech translation

• Added Czech translation, thanks to @Ghost4Man!

Polish translation

• Added Polish translation, thanks to @komaedalove!

General polish

• Enabled smaller step intervals for filter values so that you can tune settings more precisely.
• Improved display of gamma value.
• Facilitated extension translation via https://lusito.github.io/web-ext-translator/?gh=https://github.com/PyvesB/night-video-tuner
• Optimised images so that the extension menu loads faster.
• Removed update notification so that the extension requires less permissions.
• Opera is no longer officially supported (see #2), but you can still install the extension via Install Chrome Extensions.
• Various other improvements and cleaning up.

Gamma filter

• Implemented new gamma filter.
• Various other tweaks.

Tests and clean-up

● Several under the hood enhancements.
● Added tests to improve maintainability.

Outline fixes

• Fixed selected elements outline in some browsers.