ci: Update building plugin => Node.js v20 + create pull request

[SRWieZ]

This pull request updates the GitHub Actions workflow for building the plugin.

• Updated the Node.js version from 18.x to 20.x.
• Updated stefanzweifel/git-auto-commit-action to run on pull requests, allowing for faster testing of proposed changes.
• Added peter-evans/create-pull-request on the main branch to ensure it builds even after squashing and merging.

[PeteBishwhip]

Just wondering, but is it worth having the plugin build no longer target pull_request at all and only on changes to main? We avoid noisy commits and we can merge in that single PR prior to release with all the changes merged between X and Y?

[SRWieZ]

I just updated my description. I propose the following:

• Auto building on the pull request to test the changes, as I prefer checking the code and testing it in my app when possible.
• Auto building on the main branch, because after merging, the plugin also needs to be rebuilt.