chore: add pull_request_template (#86)

* chore: add pull_request_template

* refactor: relocate contributing guide

* doc: updated README

* patch: use background as default heading

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,21 @@
+<!-- NOTE: Please read the CONTRIBUTING.md guidelines before submitting your patch, and ensure you followed them all: https://github.com/daeuniverse/dae/blob/master/CONTRIBUTING.md -->
+
+### Background
+
+<!--- Why is this change required? What problem does it solve? -->
+
+### Checklist
+
+- [ ] The Pull Request has been fully tested
+- [ ] There's an entry in the CHANGELOG
+- [ ] There is a user-facing docs PR against https://github.com/daeuniverse/dae
+
+### Full changelog
+
+- [Implement ...]
+
+### Issue reference
+
+<!--- If it fixes an open issue, please link to the issue here. -->
+
+Fix #_[issue number]_

README.md

@@ -52,7 +52,7 @@ See [How it works](docs/how_it_works_zh.md).
 
 ## Contributors
 
-Special thanks goes to all [contributors](https://github.com/daeuniverse/dae/graphs/contributors). If you would like to contribute, please see the [instructions](./docs/contribute.md). Also, it is recommended following the [commit-msg-guide](./docs/commit-msg-guide.md).
+Special thanks goes to all [contributors](https://github.com/daeuniverse/dae/graphs/contributors). If you would like to contribute, please see the [instructions](./CONTRIBUTING.md). Also, it is recommended following the [commit-msg-guide](./docs/commit-msg-guide.md).
 
 ## License