docs: add contributing guide

CONTRIBUTING.md

+# Contributing
+
+# Getting Started
+
+[Install][bazelisk-install] `bazelisk` and run the tests:
+
+```sh
+$ bazelisk test //...
+$ (cd e2e; bazelisk test //...)
+```
+
+Set up Git hooks:
+
+```sh
+$ bazelisk run //tools/git/hooks:install
+```
+
+[bazelisk-install]: https://github.com/bazelbuild/bazelisk?tab=readme-ov-file#installation
+
+# Workflow
+
+- Follow the [contributions guide] to be granted forking permissions.
+- [Fork] the project
+- Implement the change
+- [Create merge request] from fork
+
+# Release
+
+`semantic-release` performs automatic releases of the project.
+
+Release channels for `alpha`, `beta` and `stable` releases are used.
+
+The [upstream configuration usage guide][semrel-release-channels-usage] provides information on how to perform a
+release.
+
+[semrel-release-channels-usage]: https://gitlab.arm.com/semantic-release/config-release-channels/-/blob/main/README.md?ref_type=heads#usage
+[contributions guide]: https://gitlab.arm.com/documentation/contributions#contributions
+[Fork]: https://docs.gitlab.com/ee/user/project/repository/forking_workflow.html#create-a-fork
+[Create merge request]: https://docs.gitlab.com/ee/user/project/repository/forking_workflow.html#merge-changes-back-upstream