docs: re-add release documentation markdown file

In uppercase for consistency with the other root-level markdown files.

Signed-off-by: Dan Luhring <dluhring@chainguard.dev>

RELEASE.md

@@ -0,0 +1,19 @@
+# Melange Release Process
+
+To cut a release:
+
+1. Go to https://github.com/chainguard-dev/melange/actions/workflows/release.yaml.
+2. Click on the `Run workflow` button.
+3. In the dropdown, ensure that the `main` branch is selected.
+4. In the dropdown, click on the `Run workflow` button.
+5. Wait for the workflow to complete successfully.
+
+### Useful things to know
+
+#### Detecting whether a new release is needed
+
+The release workflow checks to see if there are any changes since the last release. If there are no changes, the workflow will end execution early and not create a new release.
+
+#### Automatic triggering
+
+In addition to being triggerable manually (as described at the top of this document), the workflow also runs automatically every Monday at midnight UTC. Just like with manual triggering, if there are no new changes since the last release, the workflow will end early without creating a new release.