add release docs

RELEASING.md

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+# Checklist for releasing WireMock
+
+- [ ] Bump version number
+- [ ] Publish the release note
+- [ ] Update the version on wiremock.org
+- [ ] Announce on the WireMock Community Slack
+- [ ] Announce on social
+
+## Pre-release - bump version number
+Make sure the version number has been updated. Update the version number and commit and push.
+
+## Publish the release note
+Release drafter should have created a draft release note called "next". Check it for sanity and edit it to add any additional information and then set the tag
+to the version you've just released and publish it.  
+
+This will trigger the [Release workflow](https://github.com/wiremock/wiremock-grpc-extension/blob/main/.github/workflows/release.yml)
+and publish the new release.
+
+## Update the version on wiremock.org
+https://github.com/wiremock/wiremock.org
+
+Publish the changes by merging to the `live-publish` branch and manually triggering the "Deploy Jekyll site to Pages" workflow.
+
+## Post an announcement on the WireMock Community Slack
+Announce in the #announcments channel then link to the message from #general.
+
+## Shout about it on as many social media platforms as possible
+You know the drill.