4.0.0 release

[JeroenDeDauw]

We have not had a proper release since 3.0.0 in 2018.

https://github.com/SemanticMediaWiki/SemanticFormsSelect/blob/master/RELEASE-NOTES.md

And we had a bunch of changes by @gesinn-it-evl @gesinn-it-gea and @gesinn-it-wam since: 4.0.0-beta...master

[gesinn-it-gea]

We are using master in production for a long time without issues. To my opinion it's okay to make a new release.

[marksteward]

This has been in beta for almost 2 years. Can it get a version bump please?

[jaideraf]

Bump :)

[JeroenDeDauw]

#136

[JeroenDeDauw]

To speed this up next time, make some PRs that add release notes