Add TS to PR checklist (#294)

Author: alexkrolick

.github/PULL_REQUEST_TEMPLATE.md

@@ -36,6 +36,7 @@ merge of your pull request!
 
 - [ ] Documentation
 - [ ] Tests
+- [ ] Typescript definitions updated
 - [ ] Ready to be merged
       <!-- In your opinion, is this ready to be merged as soon as it's reviewed? -->
 - [ ] Added myself to contributors table