docs: add RELEASE.md file to describe release process.

Signed-off-by: Adam Talbot <[email protected]>

RELEASE.md

@@ -0,0 +1,17 @@
+# Releases
+
+## Schedule
+
+The release schedule for cert-manager is defined on the [cert-manager website](https://cert-manager.io/docs/releases/).
+
+## Process
+
+The release process is descibed in detail on the [cert-manager website](https://cert-manager.io/docs/contributing/release-process/).
+
+## Artifacts
+
+The cert-manager project will produce the following artifacts each release. For documentation on how those artifacts are produced see the "Process" section.
+
+- *Container Images* - Container images for the cert-manager project are published for all cert-manager components. 
+- *Helm chart* - An offical Helm chart is mainained within this repo and published to `charts.jetstack.io` on each cert-manager release.
+- *Binaries* - Until version 1.15 the cmctl binary was maintained within this repo and published as part of the cert-manager release. For releases after 1.15 the CLI has moved to its [own repository](https://github.com/cert-manager/cmctl). Binary builds are still avaiable for download from this new location.