Add PR template

doc/dev.md

@@ -1,5 +1,48 @@
 # Dev
 
+## Workflow
+
+### Start with an issue before writing code
+
+Before writing any code, please create an issue first that describes the problem
+you are trying to solve with alternatives that you have considered. A little bit
+of prior communication can save a lot of time on coding. Keep the problem as
+small as possible. If there are two problems, make two issues. We discuss the
+issue and if we reach an agreement on the approach, it's time to move on to a
+PR.
+
+### Follow up with a pull request
+
+Post a corresponding PR with the smallest change possible to address the
+issue. Then we discuss the PR, make changes as needed and if we reach an
+agreement, the PR will be merged.
+
+### Tests
+
+Each bug fix, change or new feature should be tested well to prevent future
+regressions.
+
+### Force-push
+
+Please do not use `git push --force` on your PR branch for the following
+reasons:
+
+- It makes it more difficult for others to contribute to your branch if needed.
+- It makes it harder to review incremental commits.
+- Links (in e.g. e-mails and notifications) go stale and you're confronted with:
+  this code isn't here anymore, when clicking on them.
+- CircleCI doesn't play well with it: it might try to fetch a commit which
+  doesn't exist anymore.
+- Your PR will be squashed anyway.
+
+## Developing
+
+Run `bb dev` to start shadow-cljs compilation in watch mode. Then run `node out/nbb_main.js` to invoke nbb.
+
+## Testing
+
+You can run tests using `bb run-tests` and `bb run-integration-tests`.
+
 ## Release
 
 Static files including compiled JS are hosted on Github. This is set up like