[Vue] use .development suffix for watch files and gitignore them #18286

Description:

I noticed in the Vue workflow, when running vue:build --watch, the UMD files are overwritten. This causes git to notice and requires a vue:build before a dev can push. This PR changes the output file name of files built with --watch to have a .development suffix and adds paths like these to the .gitignore so rebuilding JS locally before pushing isn't always needed.

Review

• [ ] Functional review done
• [ ] Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• [ ] Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• [ ] Security review done
• [ ] Wording review done
• [ ] Code review done
• [ ] Tests were added if useful/possible
• [ ] Reviewed for breaking changes
• [ ] Developer changelog updated if needed
• [ ] Documentation added if needed
• [ ] Existing documentation updated if needed

I think this is good merge, will fix the conflicts 👍

Unfortunately it won't fix the conflicts with production JS, just means committing/pushing locally will be a bit easier.