add automated publishing

.github/workflows/publish.yml

+name: Publish to pub.dev
+
+on:
+  push:
+    tags:
+      - 'v[0-9]+.[0-9]+.[0-9]+*'
+
+jobs:
+  publish:
+    permissions:
+      id-token: write # Required for authentication using OIDC
+    uses: dart-lang/setup-dart/.github/workflows/publish.yml@v1
+    # with:
+    #   working-directory: path/to/package/within/repository
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