chore(github): add PR template (#1394)

Author: huyenltnguyen

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,14 @@
+Checklist:
+
+<!-- Please follow this checklist and put an x in each of the boxes, like this: [x]. It will ensure that our team takes your pull request seriously. -->
+
+- [ ] I have read and followed the [contribution guidelines](https://contribute.freecodecamp.org).
+- [ ] I have read and followed the [how to open a pull request guide](https://contribute.freecodecamp.org/how-to-open-a-pull-request/).
+- [ ] My pull request targets the `main` branch of the repo.
+- [ ] I have tested these changes locally on my machine.
+
+<!--If your pull request closes a GitHub issue, replace the XXXXX below with the issue number.-->
+
+Closes #XXXXX
+
+<!-- Feel free to add any additional description of changes below this line -->