Fuzzy finder: reduce content width when filenames are short

Created by: olafurpg

Currently, the fuzzy finder content view uses 80% of the window width (CSS width: 80wv). This is sometimes looks awkward in repositories that only have filenames that are short. It would be nice if the content view was less wide when possible.

Originally posted by @rrhyne in https://github.com/sourcegraph/sourcegraph/issues/21201#issuecomment-862778102

@olafurpg in repsonse to @tsenart's comment on width, we would need to reduce width overall for the entire window, then ensure line breaking looks ok for the list elements. Here's a quick preview that isn't entirely correct (we would want to address lineheight of the wrapped item, vs. margin between elements) but gives you an idea of what that would look like. Tomás, would this solve your issue with the width?

If we like this, a more careful effort than I have time for would analyze the width of file paths in a few repositories so that we may more carefully consider the width of the modal.