ci: group dependabot prs and run lint&build for every push&pr

[northword]

closes: #222

• dependabot: merge all PRs for non-major updates, less intrusive!
• Run lint/build at push/pr: this is especially useful for pr, to quickly see if contributors' code is compliant with lint requirements, and if dependency changes are clearly breaking the build.

[windingwind]

How about adding a no-op test so that other plugins can copy?

[northword]

Recently, I've been working on some Scaffold documentation, so if someone needs it, they should be able to quickly configure it according to the documentation.

We can add a job in the CI file to run the test (comment it), and add the necessary documentation, so that users can use the Action after uncommenting it.

For the test itself, there doesn't seem to be much modification if you don't give the test case file? (except that the test script in package.json is changed to zotero-plugin test)

Also, if it's added, I think it should be added after Scaffold goes to 0.2, not now (since the API/Config may still change).