chore: create contributing docs

Author: NeoIsRecursive

.github/CONTRIBUTING.md

@@ -0,0 +1,22 @@
+# How to contribute to statamic-backup
+
+## Found a bug?
+
+Please do create an issue, or upvote/add more information to an existsing issue for that bug!
+
+When creating issues, please include the exception that was thrown or if you did some troubleshooting - what you found! :)
+
+## Security issue?
+
+Please send an email to [email protected] with the issue.
+
+## Want to contribute with a pull request?
+
+Fantastic, we appreciate it!
+
+1. Make sure the test-and-lint-suite passes, this can be run locally with `composer qa`.
+2. Name your PR according to [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/), the reason for using conventional commits is so we can generate changelogs/release notes. Some examples:
+   - `fix: backup failing due to xyz`
+   - `feat: add new feature xyz`
+
+And that is everything, happy coding!