Add migrate old settings button

[LiliaDoe]

• Should be a fix for those who's settings didn't migrate
• Working on a fix to migrate options function too

[LiliaDoe]

localStorage returns undefined, and I'm not sure if that's fixable. I'm closing this until this I figure that out

[LiliaDoe]

I figured out the storage system for a temporary addon was different than a signed addon in firefox, which caused my error. After fixing that part, the manual migrate button worked as expected.

That said, if you could look through the option for it to make sure it looks how you'd like it, that'd be great! I added a warning to the button, since pressing it will overwrite the user's current settings:

If you think the warning unnecessary, I'll take it off. It's in the tooltip as well, so it might be redundant

[sonarqubecloud]

Quality Gate failed

Failed conditions
7.7% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud

[extesy]

Looks great, thank you!