chore: add CONTRIBUTING.md

We place some assumptions on the code coming in to the project and it
is better if these are visible somewhere so we don't have to repeat it
in every PR.

CONTRIBUTING.md

@@ -0,0 +1,36 @@
+# Contributing
+
+Thanks for showing interest in contributing to [CAN-go]!
+
+## Suggesting Features
+
+Before creating a PR, please consider that [CAN-go] is a tool that Einride uses
+internally and as such, features that are not aligned with how we are using CAN
+will probably not be accepted. In that case feel free to fork our project and
+make the changes you want there instead.
+
+## Reporting Issues
+
+If you find a bug, please create an
+[issue](https://github.com/einride/can-go/issues) for it, or create a PR
+following the [Pull Request Guidelines](#pull-request-guidelines).
+
+## Development
+
+To start developing on [CAN-go] it is enough to clone the repo and run `make`.
+
+## Pull Request Guidelines
+
+[CAN-go] is using the
+[Conventional Commits](https://www.conventionalcommits.org/) commit message
+convention.
+
+Keep your commits as small as possible, but still keep all changes related to a
+logical change in the same commit. When receiving review feedback, fix up the
+commits with the changes addressing the feedback and force-push, please don't
+send fix commits.
+
+Before opening a PR, please make sure you get no errors when running `make` and
+that there is sufficient test coverage for added or changed functionality.
+
+[can-go]: https://go.einride.tech/can