Suggestion: CI step fail if any file coverage decrease

[TSMMark]

Is your feature request related to a problem? Please describe. While reviewing a PR from a teammate, I'd love to know that their changes are not decreasing Ts coverage on any file

Describe the solution you'd like compare TS coverage per file on current branch vs base branch and report delta

Describe alternatives you've considered

Additional context Thank you so much for this package — originally coming over from flow several years ago, I've really missed this feature. Very excited to implement type-coverage checks once again!