chore(github): add types to PULL_REQUEST_TEMPLATE.md checklist

Author: remarkablemark

.github/PULL_REQUEST_TEMPLATE.md

@@ -23,6 +23,7 @@ To check an item, place an "x" in the box like so: `- [x] Tests`
 
 - [ ] Tests
 - [ ] Documentation
+- [ ] Types
 
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