Add glob pattern support to `--ignore`

[marfl]

Replaces the existing path-based ignore logic with glob patterns using the globset crate.

Addresses #96

I'm not sure how (and where) to best add tests for this change.

Note that this PR adds some asymmetry with how paths are handled in trunk: ignores are now based on globs, but everything else still needs to be provided as a specific path, and trunk often (always?) fails if such paths don't exist.

Checklist

• [x] Updated CHANGELOG.md describing pertinent changes.
• [ ] Updated README.md with pertinent info (may not always apply). :: I don't think we need to?
• [ ] Updated site content with pertinent info (may not always apply). :: I don't think we need to?
• [x] Squash down commits to one or two logical commits which clearly describe the work you've done. If you don't, then Dodd will 🤓.