[internal] Improve release script further

[HenriBeck]

What would you like to add/fix?
Improve release script further.

This adds:

• A script for creating a GitHub release.
• Improve output of updating changelog script.

Corresponding issue (if exists): #984

[HenriBeck]

@kof please review.

Flow would be like this now:

yarn release:minor

And then

yarn create-github-release

[kof]

Why not in one step?

[HenriBeck]

Yeah, makes sense, moved it to postrelease