chore: add prefix info to the PR template

.github/PULL_REQUEST_TEMPLATE.md

@@ -3,4 +3,16 @@ When submitting a new feature or fix:
 
 - Add a new entry to the CHANGELOG - https://github.com/PostgREST/postgrest/blob/main/CHANGELOG.md#unreleased
 - If relevant, update the docs     - https://github.com/PostgREST/postgrest-docs
+- Use a prefix for the PR title or commits, e.g. "fix: description of the fix".
+  + `fix`, bug fixes
+  + `feat`, new features added
+  + `perf`, performance improvements
+  + `nix`, related to the Nix development environment
+  + `ci`, related to the Continuous Integration modules
+  + `test`, related to the testing modules
+  + `refactor`, refactoring code
+  + `deprecate`, deprecating a feature
+  + `chore`, maintenance (changelog, build process, etc.)
+  + Other prefixes may be used if necessary
+- If there's a breaking change, add `BREAKING CHANGE` and an explanation to your commit message
 -->