Add releasing docs and release GitHub workflow

.github/workflows/release.yml

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+name: release
+
+on:
+  push:
+    tags: [ 'v*' ]
+
+permissions:
+  contents: read
+
+jobs:
+  godoc:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Wait 1 minute
+        # make sure that new the tag is available for pkg.go.dev
+        run: sleep 60
+      - name: Update pkg.go.dev
+        run: curl https://proxy.golang.org/github.com/${{ github.repository }}/@v/${{ github.ref_name }}.info

RELEASING.md

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+# Release Process
+
+1. Add and push a signed tag:
+
+   ```sh
+   TAG='v<version>'
+   COMMIT='<commit-sha>'
+   git tag -s -m $TAG $TAG $COMMIT
+   git push upstream $TAG
+   ```
+
+1. Create a GitHib Release named `<version>` with `v<version>` tag.
+
+   The release description should include all the release notes
+   from the [`CHANGELOG.md`](CHANGELOG.md) for this release.