feat: permissions (#168)

- Load `app-permissions` from schema exported by `@octokit/openapi`
- Update documentation in README.md
- Implement the `permissions_*` inputs in the action code

---------

Co-authored-by: Parker Brown <17183625+parkerbxyz@users.noreply.github.com>

CONTRIBUTING.md

@@ -0,0 +1,15 @@
+# Contributing
+
+Initial setup
+
+```console
+npm install
+```
+
+Run tests locally
+
+```console
+npm test
+```
+
+Learn more about how the tests work in [test/README.md](test/README.md).