chore: add docs about release branches and how to release a new version

Signed-off-by: Yordis Prieto <[email protected]>

CONTRIBUTING.md

@@ -22,13 +22,13 @@
 
 1. Open `config/provider.go` file.
    1. Find `ExternalNameConfigs` variable.
-   2. Add new resource terraform resource name to the `ExternalNameConfigs` map.
-   3. Find `GetProvider` function.
-   4. Add a new `AddResourceConfigurator` function call with the new resource name using
+   1. Add new resource terraform resource name to the `ExternalNameConfigs` map.
+   1. Find `GetProvider` function.
+   1. Add a new `AddResourceConfigurator` function call with the new resource name using
       1. Add the `r.ShortGroup` to the resource.
-      2. Add (if any) all the `r.References` to the resource.
-2. Run `make generate` to generate the new resource configuration.
-3. Run `make k-apply-crds` to apply the new CRDS.
+      1. Add (if any) all the `r.References` to the resource.
+1. Run `make generate` to generate the new resource configuration.
+1. Run `make k-apply-crds` to apply the new CRDS.
 
 #### Test the new resource
 
@@ -39,8 +39,49 @@ Or to be safe, you call apply all the required resources at once:
 
 1. `k-apply-all`
 
+### Releasing a New Version
+
+1. [Create Release Branch](#creating-a-release-branch) or [Patch a Release Branch](#patching-a-release-branch) the
+  [Release Branch](#release-branches).
+1. Visit [Tag Workflow Action](https://github.com/crossplane-contrib/provider-upjet-digitalocean/actions/workflows/tag.yaml)
+and click on the `Run workflow` button. Make sure the "Branch" is set to the release branch, e.g., `release-0.2`.
+Enter the version number in the "Release version" field, e.g., `v0.2.1`, and a sensible value for the "Tag message"
+field. Verify the information and click the "Run workflow" button.
+1. Wait for the Tag Workflow Action to complete.
+1. Run the [CI Workflow Action](https://github.com/crossplane-contrib/provider-upjet-digitalocean/actions/workflows/ci.yml)
+   by clicking on the "Run workflow" button. Make sure the "Branch" is set to the release branch, e.g., `release-0.2`.
+1. Create a new GitHub Release
+   at [New Release](https://github.com/crossplane-contrib/provider-upjet-digitalocean/releases/new).
+   Select the tag that was created by the Tag Workflow Action, e.g., `v0.0.1`, and enter the release notes. Make sure the Target branch is set to the release branch, e.g., `release-0.2`. Click the "Publish release" button.
+
 ## Explanations
 
+### Release Branches
+
+Release branches are prefixed with `release-` followed by the version number, e.g., `release-0.2`. The version number
+should be composed by the major and minor version numbers, e.g., `0.2`. The patch version number should never be part
+of the release branch name.
+
+Reuse the existing release branch, backport fixes to the existing major/minor branch.
+
+#### Creating a Release Branch
+
+Create or patch the [Release Branch](#release-branches) from the `main` branch. You could use visit [Branches](https://github.com/crossplane-contrib/provider-upjet-digitalocean/branches)
+and click on the `New branch` button, or use the following commands:
+
+```shell
+git checkout -b release-<MAJOR>.<MINOR>
+git push origin release-<MAJOR>.<MINOR>
+```
+
+#### Patching a Release Branch
+
+To apply a patch to a release branch, you should tag the pull request with the
+backport label, eg. `Backport release-0.2`. The pull request will be merged into
+the release branch.
+
+### Make Commands
+
 Run code-generation pipeline:
 
 ```console