* Ädd support for IINA
* cleanup
* Add start background image
* Restore comment
* Support custom player path
* Update messages
* Separate IINA changes from python_mpv_jsonipc
* Do not show file info for our placeholder image in the UI
* Fix mpv socket
* Fix running IINA from frozen app
Apparently, `iina-cli` gets confused when launched from a frozen app
and automatically adds `--stdin` to its passed launch arguments.
But then, it waits for a file to be piped and, because there is none,
the player crashes almost immediately. Sending `--no-stdin` to the
process resolves the ambiguity and does not cause any harm if
Syncplay is started from sources.
* Pass again environment to the subprocess.Popen call that opens mpv
Related to: c07206c18992c1dca401b30a01b9f0fe54a71df5
9de3b4d86f