Add releasing guide (#2403)

Author: arybolovlev

RELEASING.md

@@ -0,0 +1,55 @@
+# Releasing
+
+The purpose of this document is to outline the release process for the Kubernetes Provider for Terraform.
+
+The Semantic Versioning agreement is being followed by this project. Further details can be found [here](https://semver.org/).
+
+## How To Release
+
+To create a new release, adhere to the following steps:
+
+- Decide on the version number that you intend to release. Throughout the following steps, it will be denoted as `<SEMVER>`.
+
+- Switch to the `main` branch and fetch the latest changes:
+
+  ```console
+  $ git switch main
+  $ git pull
+  ```
+
+- Create a new branch from the `main`. The branch name is required to adhere to the following template: `release/v<SEMVER>`.
+
+  ```console
+  $ git checkout -b release/v<SEMVER>
+  ```
+
+- Generate change log entries:
+
+  ```console
+  $ make changelog
+  ```
+
+- Update the [`CHANGELOG`](./CHANGELOG.md) file with the output produced in the previous step preceded by the release version and the planned release date expressed as `Mon DD, YYYY` format. The version number in this file must correspond with the `<SEMVER>` of the release branch name.
+
+- Create a pull request against the `main` branch and follow the regular code review and merge procedures.
+
+- After merging the release branch into the `main` one, a git tag with the new release version number needs to be attached to the release commit to start a release process. The version number in the tag must correspond with the `v<SEMVER>` of the merged release branch name. Below is an example of the commands that need to be run in this step:
+
+  ```console
+  $ git switch main
+  $ git pull
+  $ git log --pretty=oneline -n 1
+
+  ccd98a787308e6887c97291652430bd083106ccb (HEAD -> main, ...) v<SEMVER> (#XXXX)
+
+  $ git tag v<SEMVER> ccd98a787308e6887c97291652430bd083106ccb
+  $ git log --pretty=oneline -n 1
+
+  ccd98a787308e6887c97291652430bd083106ccb (..., tag: v<SEMVER>) v<SEMVER> (#XXXX)
+
+  $ git push origin v<SEMVER>
+  ```
+
+- Confirm this succeeded by viewing the repository [tags](https://github.com/hashicorp/terraform-provider-kubernetes/tags).
+
+- Monitor the [release](https://github.com/hashicorp/terraform-provider-kubernetes/actions/workflows/release.yaml) action on GitHub. Once it is completed, a new release should be available on the [registry](https://registry.terraform.io/providers/hashicorp/kubernetes/latest) portal within 15-30 minutes. If this does not happen or the action fails, please reach out to the release engineering team to troubleshoot the issue.