Fixes to get ready release 3.x

[mkszepp]

Some minimal adjustments for next version

[mkszepp]

I will try to find later some time to fix some points in readme... i have seen that some links are not correctly linked right now or are ending in an 404 (for example upgrade.md is missing...).
In additional i will try to upgrade one of my app to version v3.x before we do 3.x release.

[robmadole]

Thanks for fixing the link I missed!

[mkszepp]

@robmadole the typing is right now incorrect for parse.icon. In my convert i did think, that it was a mistake inside this project, but now i have detected that the addon wasn't working correctly.

I have seen that this issue was already reported ~ a year ago FortAwesome/Font-Awesome#20231
It would be good to fix this, so we can remove in any future the @ts-expect-error rule in this project

Possible fix for this bug see FortAwesome/Font-Awesome#20557

fyi: i have added a test for non default prefix now... so we will never run again into this bug