docs: document the release flow (#4754)

Co-authored-by: Asher Gomez <ashersaupingomez@gmail.com>

.github/RELEASE.md

@@ -0,0 +1,25 @@
+This document describes the release flow of the Standard Library for the
+maintainers. If you're not a maintainer, you don't need to read this document.
+
+# The Release Flow
+
+To cut a release, follow the below steps:
+
+1. Message the Slack `#std` and Discord `#dev-std` channels "🔒 std is locked".
+1. Trigger `version_bump` action with `main` branch selected.
+1. Wait for @denobot to create a release PR. Note: the tool automatically
+   calculates the necessary version upgrades.
+1. Review PR, and update it if necessary.
+1. Land the PR.
+1. Tag the main branch with `release-YYY-MM-DD` (this step can be automated in
+   the future):
+
+   ```
+   git tag release-YYYY.MM.DD
+   git push origin release-YYYY.MM.DD
+   ```
+
+1. Publish the tag from github UI (Re-check the tag is in correct form).
+1. Wait for `workspace publish` action to publish the new versions to JSR.
+1. Message the Slack `#std` and Discord `#dev-std` channels "🔓 std is unlocked
+   <url_of_release>".