Filter changed files

This version includes some great work by @andybelltree!
You can now:

• Filter the coverage report to only show files that are changed in the PR
• Delete old coverage comments

What's Changed

• Add a default value for github-token input. by @jackton1 in #22
• Filter changed files by @andybelltree in #31

New Contributors

• @jackton1 made their first contribution in #22
• @andybelltree made their first contribution in #31

Full Changelog: v0.2.21...v0.3.1