chore: update PR template

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,9 +1,22 @@
-First of all, thanks for your contribution! :-)
+First of all, thank you for your contribution! :-)
 
-Please makes sure these boxes are checked before submitting your PR, thank you!
+Please makes sure that these checkboxes are checked before submitting your PR, thank you!
 
-* [ ] Make sure you propose PR to correct branch: bugfix for `master`, feature for latest active branch `feature-x.x`.
-* [ ] Make sure you follow antd's [code convention](https://github.com/ant-design/ant-design/wiki/Code-convention-for-antd).
+* [ ] Make sure that you propose PR to right branch: bugfix for `master`, feature for latest active branch `feature-x.x`.
+* [ ] Make sure that you follow antd's [code convention](https://github.com/ant-design/ant-design/wiki/Code-convention-for-antd).
 * [ ] 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.
+
+Extra checklist:
+
+**if** *isBugFix***:**
+
+  * [ ] Make sure that you add at least one unit test for the bug which you had fixed.
+
+**elif** *isNewFeature***:**
+
+  * [ ] Update API docs for the component.
+  * [ ] Update/Add demo to demonstrate new feature.
+  * [ ] Update TypeScript definition for the component.
+  * [ ] Add unit tests for the feature.