docs: Add RELEASE.md documentation (#867)

RELEASE.md

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+# Release Process
+
+## Overview
+
+The Karpenter project is an SIG autoscaling project that has the following two components:
+- Kubernetes Custom Resource Definitions (CRDs)
+- Corresponding Go API in the form of [`sigs.k8s.io/karpenter`](https://pkg.go.dev/sigs.k8s.io/karpenter) Go package
+
+This repository is the home for both of the above components.
+
+## Versioning Strategy
+
+The versioning strategy for this project is covered in detail in [the release type section of the compatability documentation](https://karpenter.sh/docs/upgrading/compatibility/#release-types).
+
+## Releasing a New Version
+
+The following steps must be done by one of the [Karpenter Maintainers](https://github.com/kubernetes/org/blob/main/config/kubernetes-sigs/sig-autoscaling/teams.yaml):
+
+For a **MAJOR**, **MINOR**, or **RC** release:
+- Verify the CI tests pass before continuing.
+- Create a tag using the current `HEAD` of the `main` branch by using `git tag v<major>.<minor>.<patch>`
+- Push the tag to upstream using `git push upstream v<major>.<minor>.<patch>`
+- This tag will kick-off the [Release Workflow](https://github.com/kubernetes-sigs/karpenter/actions/workflows/release.yaml) which will auto-generate release notes into the repo's [Github releases](https://github.com/kubernetes-sigs/karpenter/releases).
+
+For a **PATCH** release:
+- Create a new branch in the upstream repo similar to `release-v<major>.<minor>.x` that's checked out from the latest released tag from `HEAD` on `v<major>.<minor>` if one doesn't already exist.
+- Create a branch in your fork (origin) repo similar to `<githubuser>/release-v<major>.<minor>.<patch>`. Use the new branch
+  in the upcoming steps.
+- Use `git` to cherry-pick all relevant PRs into your branch.
+- Create a pull request of the `<githubuser>/release-v<major>.<minor>.<patch>` branch into the `release-v<major>.<minor>.x` branch upstream. Wait for at least one maintainer/codeowner to provide a `lgtm`.
+- Verify the CI tests pass and merge the PR into `release-v<major>.<minor>.x`.
+- Create a tag using the `HEAD` of the `release-v<major>.<minor>.x` branch by using `git tag v<major>.<minor>.<patch>`
+- Push the tag to upstream using `git push upstream v<major>.<minor>.<patch>`
+- This tag will kick-off the [Release Workflow](https://github.com/kubernetes-sigs/karpenter/actions/workflows/release.yaml) which will auto-generate release notes into the repo's [Github releases](https://github.com/kubernetes-sigs/karpenter/releases).