Implement version check in GHA

[sebastian-peter]

It should work similarly to how it was done with Jenkins.

Normally, dev version should be higher than the one in main. After merging dev, versions in main and dev should be the same (shortly). When merging back changes of the release from main to dev, the snapshot version should increase again.

main | dev
0.5.0 | 0.6.0 <- Before release
0.6.0 | 0.6.0 <- After release PR has been merged
0.6.0 | 0.7.0 <- After changes from main have been merged back to dev

This means:

• For PRs merging onto main (from dev), versions in dev and main should be equal
• For PRS merging onto dev (from feature branches), version should stay the same
• When the pipeline runs for dev or main itself, no version check should occur.