re-add (updated version of) push-templates-tag to release.yml

Unlike the original version, this one does not depend on the Go SDK automation
and instead derives the template tag name from the Spin version tag name.

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

.github/workflows/release.yml

@@ -254,6 +254,27 @@ jobs:
             --title ${{ github.ref_name }} \
             --generate-notes ${{ env.PRERELEASE }}
 
+  push-templates-tag:
+    runs-on: ubuntu-latest
+    if: startsWith(github.ref, 'refs/tags/v')
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set the tag to spin/templates/v*
+        shell: bash
+        run: |
+          spin_tag=$(echo "${{ github.ref }}" | grep -Eo "refs/tags/v[0-9.]+")
+          IFS=. read -r major minor patch <<< "${spin_tag}"
+          echo "TEMPLATE_TAG=spin/templates/$major.$minor" >> $GITHUB_ENV
+
+      - name: Tag spin/templates/v* and push it
+        shell: bash
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          git tag ${{ env.TEMPLATE_TAG }} -f
+          git push origin ${{ env.TEMPLATE_TAG }} -f
+
   ## statically linked spin binaries
   build-spin-static:
     name: Build Spin static