docs: added release process (#827)

Signed-off-by: Kostis Kapelonis <kostis@codefresh.io>

docs/contributing/releasing.md

@@ -0,0 +1,63 @@
+# Releasing
+
+Argo Image Updater is released in a 2 step automated fashion using GitHub actions. The release process takes about 20 minutes, sometimes a little less, depending on the performance of GitHub Actions runners.
+
+Releases can only be done  by people that have write/commit access on the Argo Image Updater GitHub repository.
+
+## Introduction
+
+First install on your workstation the following:
+
+1. GoLang 
+1. The `git` executable
+1. The [GitHub CLI](https://cli.github.com/)
+1. The `semver` cli with `go install github.com/davidrjonas/semver-cli@latest`
+
+Then create a release branch:
+
+```
+git clone git@github.com:argoproj-labs/argocd-image-updater.git
+git branch -b release-0.13
+git push origin release-0.13
+```
+
+The release name is just an example. You should use the next number from the [previous release](https://github.com/argoproj-labs/argocd-image-updater/releases). Make sure that the branch is named as `release-X.XX` though.
+
+Also note that `origin` is just an example. It should be the name of your remote that holds the upstream branch of Argo Image updater.
+
+Finally run
+
+```
+./hack/create-release-pr.sh origin
+```
+
+Again notice that the argument must match the upstream Git remote that you used before. This [command](https://github.com/argoproj-labs/argocd-image-updater/blob/master/hack/create-release-pr.sh) will automatically create a Pull Request in GitHub with the contents of the new release.
+
+## Review the pull request
+
+Visit the Pull Request that you just created in the GitHub UI. Validate the contents of the diff to see the suggested changes.
+Once you are happy with the result, approve/merge the Pull Request.
+
+Merging the Pull Request will start an [automated release process](https://github.com/argoproj-labs/argocd-image-updater/blob/master/.github/workflows/create-release-draft.yaml) that will build all the artifacts
+and create a draft release.
+
+## Publish the release
+
+You should now have a draft release or Argo Image Updater with all required artifacts attached as binaries.
+
+First, attach the release notes. [GitHub can do it automatically for you](https://docs.github.com/en/repositories/releasing-projects-on-github/automatically-generated-release-notes) by clicking the respective button
+and selecting from the drop-down menu the previous release.
+
+Finally publish the release by clicking the green button on the bottom left of the screen.
+
+You are finished!
+
+
+
+
+
+
+
+
+
+

mkdocs.yml

@@ -40,6 +40,7 @@ nav:
   - Contributing:
     - Overview: contributing/start.md
     - Developing: contributing/development.md
+    - Releasing: contributing/releasing.md    
   - Examples: examples/index.md
   - Releases ⧉: https://github.com/argoproj-labs/argocd-image-updater/releases
   - Roadmap ⧉: https://github.com/argoproj-labs/argocd-image-updater/milestones