docs: add some important information to contributing

Signed-off-by: Thomas Schuetz <thomas.schuetz@t-sc.eu>

CONTRIBUTING.md

@@ -1,5 +1,30 @@
 # Contributing
 
 ## Requirements
-
 - Golang `1.20`
+- An OpenAI API key
+  * OpenAI API keys can be obtained from [OpenAI](https://platform.openai.com/account/api-keys)
+  * You can set the API key for k8sgpt using `./k8sgpt auth key`
+- If you want to build the container image, you need to have a container engine (docker, podman, rancher, etc.) installed
+
+## Building
+Building the binary is as simple as running `go build .` in the root of the repository. If you want to build the container image, you can run `docker build -t k8sgpt -f container/Dockerfile .` in the root of the repository.
+
+## Releasing
+Releases of k8sgpt are done using [Release Please](https://github.com/googleapis/release-please) and [GoReleaser](https://goreleaser.com/). The workflow looks like this:
+
+* A PR is merged to the `main` branch:
+  * Release please is triggered, creates or updates a new release PR
+  * This is done with every merge to main, the current release PR is updated every time
+
+* Merging the 'release please' PR to `main`:
+  * Release please is triggered, creates a new release and updates the changelog based on the commit messages
+  * GoReleaser is triggered, builds the binaries and attaches them to the release
+  * Containers are created and pushed to the container registry
+
+> With the next relevant merge, a new release PR will be created and the process starts again
+
+### Manually setting the version
+If you want to manually set the version, you can create a PR with an empty commit message that contains the version number in the commit message. For example:
+
+Such a commit can get produced as follows: `git commit --allow-empty -m "chore: release 0.0.3" -m "Release-As: 0.0.3`