Monitor folder for auto conversion

[craigS89]

an auto convert function where i could select a file folder, and any any new image in the folder will be automatically converted using pre saved settings.

Example:
Given: i am a user who wishes to save space on my phone
And: i have set my camera app's folder to be auto converted
When: i take a picture and it is saved as a .jpg
Then: the jpeg is replaced with an avif version

[T8RIN]

let's move to #2118 issue