Make marking of modified submodules optional

[brettz9]

Summary

Be able to disable the reporting of modified submodules, if not on a project-by-project basis, then globally.

Motivation

In some projects, submodules are modified much less frequently (e.g., in indexeddbshim, we have W3C tests as a submodule).

In such cases, one doesn't wish to be constantly reminded about a dependency's potentially very frequent updates, when one's primary focus is just on one's own project's files and ensuring changes have been committed. While modified submodules can be useful to know about for such purposes as well, it can be distracting to have these reminders across all projects at all times.

Describe alternatives you've considered

I looked into using CSS in Atom to effectively suppress color changes for modified submodules.

If there were CSS :has() support, one might be able to leverage this with :not() to revert colors to the original, non-distinct color in cases where a repository only had modified submodules.

But without this support, I was only able to apply color changes to either all repository names or to modified submodule folders, but not to the repository name of a modified submodule (when no other modifications existed).

My only other option has been to remove a project from my tree, as I find such out-of-place reminders to be too distracting to my work.

Additional context

N/A