Make discardThreshold configurable

[farnoy]

I noticed that the discard threshold when opening folders of bookmarks is hardcoded. Would it be possible to add an option to increase it?

[Rob--W]

Yes that's possible. I started with a hard-coded value to see if it would be good enough. In the original issue that resulted in this feature (#9), someone actually asked to lower the threshold to 0. There's clearly no one-size-fits-all, so I'm favorable towards adding options to customize the setting.

The required code change is quite simple, and would be similar to https://github.com/Rob--W/dont-track-me-google/commit/d7e3d491ac990a0cc39575968d2069f8c7177c15#diff-a2661882d2a4772ee7877c2794c66d81

One thing is that the extension is localized, and that the new options page should ideally be localized as well.

[farnoy]

Thanks, I'll take a stab at it soon.