Release a new version of CADTools

[tsmock]

This adds a GH workflow that does the following:

• Creates a new tag (if run on master on ROTARIUANAMARIA)
• Clones the JOSM svn repository
• Builds JOSM
• Builds the plugin
• Runs plugin tests
• If a new tag was created, upload the plugin jar

There are two ways to create releases:

• Merge-to-master (which is implemented in this PR)
  • This is better for slower-moving plugins. If you are constantly merging changes in the future, you may want to remove the perform-revision-tagging yaml key.
• Push a new tag

Example release: https://github.com/tsmock/CADTools/releases/tag/v23
The download URL for CADTools on PluginsSource should be changed to https://github.com/ROTARIUANAMARIA/CADTools/releases/latest/download/CADTools.jar (the URL for the sample release would be https://github.com/tsmock/CADTools/releases/latest/download/CADTools.jar ).

[tsmock]

I've changed the PluginsSource to link to my fork. If/when you merge this and do a release, feel free to change it back.