chore: add PULL_REQUEST_TEMPLATE.md

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,7 @@
+First of all, thanks for your contribution! :-)
+
+Please makes sure these boxes are checked before submitting your PR, thank you!
+
+[ ] Run `npm run lint` and fix those errors before submitting in order to keep consistent code style.
+[ ] Rebase before creating a PR to keep commit history clear.
+[ ] Add some descriptions and refer relative issues for you PR.