ci: add publish workflow

.github/workflows/publish-container.yaml

@@ -0,0 +1,37 @@
+name: Publish container
+
+# These permissions are needed to assume roles from Github's OIDC.
+permissions:
+  contents: read
+  id-token: write
+
+on:
+  # TODO: Remove this. Publish on PR is only here for testing this workflow.
+  pull_request:
+    branches:
+      - 'main'
+  push:
+    branches:
+      - 'main'
+    tags:
+      - 'v*'
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Compute repo metadata
+        id: repo
+        run: |-
+          echo "name=$(basename '${{ github.repository }}')" >> $GITHUB_OUTPUT
+          echo "version=$(./scripts/version)" >> $GITHUB_OUTPUT
+      - name: Login to Google Artifact Registry
+        uses: grafana/shared-workflows/actions/login-to-gar@main
+      - name: Build container and push to GAR
+        uses: grafana/shared-workflows/actions/push-to-gar-docker@main
+        with:
+          image_name: ${{ steps.repo.outputs.name }}
+          tags: |-
+            ${{ steps.repo.outputs.version }}
+          push: true