Synchronous GM_* value API
Explore implementing synchronous api methods:
GM_getValue, GM_setValue and GM_listValues
relevant: https://github.com/quoid/userscripts/issues/167#issuecomment-975380666
I'm assuming that implementing a synchronous method can only be achieved by caching that data in the js layer.
But I wonder, do we really need to implement these synchronized methods? These were deprecated five years ago when Greasemonkey 4.0 was rewritten based on WebExtensions.
I think the biggest gain we get out of this is backwards compatibility with old userscripts that haven't been updated in a while. Authors should probably be using GM. or at the very least checking for GM_/GM. before committing to their usage.
I feel like this issue is a lot of work, for maybe little gain. I think this has lower priority than other tasks, at the moment.