File pick implementation

[PhilJbt]

It seems (I checked https://github.com/sizzlemctwizzle/GM_config/blob/master/types/index.d.ts) that the filepicker input is not supported, and there is no mention of it in the wiki.
Since I need it for a config import/export feature, I was wondering if you were planning to implement it in the future.

I'd like to take this opportunity to thank you for GM_Config, it's really very practical not to have to do this from scratch!

[PhilJbt]

As a work around, I used a button in the GM_Config which create an invisible input file picker.
But, as safety policies become ever more stringent, I wonder how many time it will keep working. I used to use a GM_registerMenuCommand to do this directly, but it recently stopped working (due to a supposedly "lack of user activation").