This pull request adds documentation on how to test payload changes when opening pull requests. This is handled by GitHub actions within our CI, this workflow will build the payloads using the appropriate repositories and branches. It will then run our acceptance tests against those changes. This requires adding GitHub labels for each corresponding payload repository. The labels will contain the payload-testing prefix, each supporting testing for an external repository:

• payload-testing-branch (https://github.com/rapid7/metasploit-payloads/)
• payload-testing-mettle-branch (https://github.com/rapid7/mettle/)

Verification

• Ensure documentation is sane
• Build documentation locally and ensure everything renders as expected (docs to build docs site locally)