chore: add pr template (ckb-js#394)

* chore(lumos): add pr template

* chore: more change type options for PR template

* chore: comment advising text

Co-authored-by: Yonghui Lin <homura.dev@gmail.com>

.github/PULL_REQUEST_TEMPLATE

@@ -0,0 +1,36 @@
+# Description
+
+<!-- Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change. -->
+
+Fixes # (issue)
+
+## Type of change
+
+Please delete options that are not relevant.
+
+- [ ] Bug fix (non-breaking change which fixes an issue)
+- [ ] New feature (non-breaking change which adds functionality)
+- [ ] Refactor (non-breaking change)
+- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
+- [ ] Documentation or Website
+- [ ] Example
+- [ ] Other
+
+# How Has This Been Tested?
+
+<!--  Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration. -->
+
+- [ ] Test A
+- [ ] Test B
+
+<!-- 
+# Checklist:
+
+- [ ] My code follows the style guidelines of this project
+- [ ] I have performed a self-review of my own code
+- [ ] I have commented my code, particularly in hard-to-understand areas
+- [ ] I have made corresponding changes to the documentation
+- [ ] My changes generate no new warnings
+- [ ] I have added tests that prove my fix is effective or that my feature works
+- [ ] New and existing unit tests pass locally with my changes
+- [ ] Any dependent changes have been merged and published in downstream modules -->