ci: add automatic release asset upload on tags

Author: vjardin

.github/workflows/build.yml

@@ -3,6 +3,7 @@ name: Build
 on:
   push:
     branches: [ main ]
+    tags: [ 'v*' ]
   pull_request:
     branches: [ main ]
 
@@ -56,3 +57,23 @@ jobs:
           path: |
             ${{ github.workspace }}/artifacts/*.uf2
             ${{ github.workspace }}/artifacts/*.hex
+
+  release:
+    needs: build
+    runs-on: ubuntu-latest
+    if: startsWith(github.ref, 'refs/tags/v')
+    permissions:
+      contents: write
+    steps:
+      - name: Download firmware artifacts
+        uses: actions/download-artifact@v4
+        with:
+          name: firmware
+          path: artifacts
+
+      - name: Upload release assets
+        uses: softprops/action-gh-release@v2
+        with:
+          files: |
+            artifacts/*.uf2
+            artifacts/*.hex