Viaplay Keyboard Shortcuts per aminoffz

Adds keyboard shortcuts to Viaplay. Natively the streaming website only supports space to pause/unpause.
This extension adds multiple features including:
- M to mute/unmute.
- F to toggle fullscreen.
- S to skip intro/recap (where applicable).
- N to quickstart next episode (available when the "Next episode" button appears.
- UP/DOWN arrow-keys to increase/decrease volume.
- T press to cycle through subtitles, hold to toggle ON/OFF

Due to limited geographical testing, this extension may or may not work on other domains than viaplay.fi such as viaplay.se, .ee and others.