Allow deleting unused files

[iandunn]

Is your proposal related to a problem?

Do not delete any of the entry files, this is a convention to remind you what your extensions could be. The build will notify you and fail if you remove any of these important files.

That reminder doesn't feel useful to me, and the resulting clutter is distracting to me, and it'd be much more satisfying to have a tidy repository.

My extension only needs to be a content script, and is very unlikely to ever need the other capabilities. If I ever did want to add one, though, I could simply copy those files over from a fresh install.

Describe the solution you'd like

Allow the files to be deleted without the build failing. I don't think that violates "convention over configuration", because the files will still all exist in the exact same locations if they're actually used.