Fix errors in publish extension workflow and add logging

[Jaifroid]

This should fix #823.

• Corrects the regexp that decides which release tags to build and push to docker
• Adds logging in the form of "echo" statements that will be visible to us in the Workflow run log

@mossroy Kindly check the bash script statements carefully with your "Linux glasses" on! I'm not very familiar with it. If it can be simplified, happy to do so.

I will create a quick test script (copy of the rewrite script in the workflow) with some sample input to be sure the rewriting works, and will test in WSL on Windows.

[Jaifroid]

I decided to move the script that replaces the version numbers in the app from the Workflow (where it is difficult to maintain and test) into a bash script in /scripts.

This runs correctly in a WSL bash, tested on Windows 10 Debian shell.

I have tested the workflow by publishing a test version to gh-pages using the manual workflow dispatch. I got this result. Hopefully the logging is more informative now. NB this did not publish to Docker, only to our test implementation on gh-pages.

[Jaifroid]

To test it yourself, ensure you run the workflow dispatch from the branch Correct-publish-extension.... and not from master (dropdown in the Action UI).

Please note that there is a difference between the version number that we put in the files and that is displayed to the user, and the value that will be used as the docker push tag. The docker push tag is actually irrelevant to us, the user will never see it. But it is significant if we are releasing a tag.

• For a release, the Docker push will only run if the release tag matches ^v*([0-9.]+)$.
• For a Workflow dispatch, the user can set it to update gh-pages or update docker. The docker push will run (if selected) regardless of the value we set for the version number in that case.

[mossroy]

I did not test but the code looks good.
I've only made some minor remarks.

[Jaifroid]

Latest regexp changes tested via test workflow, to ghpages, setting a release number of v3.3.0-testing-workflow. Initial v was successfully removed, and a version of 3.3.0-testing-workflow was set in the files, and was pushed to ghpages. I guess we won't really know for certain it's all working with Docker until we create tag for 3.3.1.

[mossroy]

OK you can merge