Add support for AniVu folder and mpv-config

[P0bo]

Currently we need to select media folder , backup folder and also for mpv-config (mpv scripts, fonts,script-opts) we need to select new file patch from mpv config for each script and script opt etc which when having many scripts is really inconvenient , if we could select a single folder for AniVu and that would contain everything will solve this issue and save a lot time .

Tis will implement a more structured, consistent folder selection and will open opportunity to adding sull support for mpv-config (fonts,scripts,script-opts etc)

[P0bo]

aniyomiorg/aniyomi#1579 (comment) , the old methood of supporting scripts doesnt work properly and for the same reason aniyomi-mpv also did the same 2 months ago .