docs: Add semantic release information and issue template

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,9 @@
+## Description
+
+<!-- Thanks for contributing to betterproto! Add a thorough explanation of what your changes do below this line: -->
+
+## Checklist
+
+- [ ] This PR targets the `rc` branch (**not** `master`).
+- [ ] [If this should release a new version to PyPI when merged] The title of the PR follows the [Angular Conventional Commit](https://www.conventionalcommits.org/) syntax (`feat:` or `fix:`, with `BREAKING CHANGE:` in the commit message body if appropriate), and clearly describes the fix or feature.
+- [ ] Documentation is updated (`README.md` and docstrings).

README.md

@@ -498,6 +498,16 @@ protoc \
 - [x] Automate running tests
 - [ ] Cleanup!
 
+
+## Release
+
+New versions are versioned and released using [Semantic Release](https://github.com/semantic-release/semantic-release). When new commits
+using the Angular Conventional Commits syntax land on `master`  or `rc`, those commits are used to determine what new version to release.
+
+All Pull Requests must target the `rc` branch; when merged into `rc` they will publish new release candidate (`rc`) versions to PyPI
+automatically. When maintainers want to publish a new full release, they simply merge `rc` into `master`. This flow ensures that features
+and fixes are published quickly and continuously rather than awaiting a manual release process.
+
 ## Community
 
 Join us on [Slack](https://join.slack.com/t/betterproto/shared_invite/zt-f0n0uolx-iN8gBNrkPxtKHTLpG3o1OQ)!