Bugfix release for Windows

For the first use after update, the name of the downloaded file will be "streaming.m3u". You will have to tell Firefox to open the file with mpv, even if you previously selected that it should do this always. If you then reload the current page (or visit another one), it shouldn't ask again.

If issues still happen on Windows, please report on GitHub or send me an E-Mail.

- context-menu added: right-click on a video or link and select "play-with"

fix permissions

- added icon for dark theme
- enabled for all platforms