docs: update master -> main

Author: isc-tleavitt

CONTRIBUTING.md

@@ -4,7 +4,7 @@ Thank you for your interest in contributing! While this project originated at In
 
 ## Submitting changes
 
-If you have made a change that you would like to contribute back to the community, please send a [GitHub Pull Request](/pull/new/master) explaining it. If your change fixes an issue that you or another user reported, please mention it in the pull request. You can find out more about pull requests [here](http://help.github.com/pull-requests/).
+If you have made a change that you would like to contribute back to the community, please send a [GitHub Pull Request](/pull/new/main) explaining it. If your change fixes an issue that you or another user reported, please mention it in the pull request. You can find out more about pull requests [here](http://help.github.com/pull-requests/).
 
 Every pull request should include at least one entry in CHANGELOG.md - see [keepachangelog.com](https://keepachangelog.com/) for guidelines.