migrate Drone CI workflow to Gitea Actions

.drone.yml

@@ -1,11 +0,0 @@
-kind: pipeline
-type: docker
-name: default
-
-steps:
-  - name: build-firmware
-    image: stklcode/avr-toolchain
-    commands:
-      - avr-gcc --version
-      - cd firmware
-      - make compile info

.github/workflows/build.yml

@@ -0,0 +1,28 @@
+---
+name: Build Firmware
+
+on: [push, pull_request]
+
+jobs:
+  build-firmware:
+    name: Compile
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup AVR-GCC
+        run: |
+          apt-get update
+          apt-get install --no-install-recommends -y gcc-avr binutils-avr avr-libc
+
+      - name: Compile
+        working-directory: firmware
+        run: make compile info
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          path: firmware/*.hex
+        if: ${{ gitea.event_name == 'push' && gitea.ref_name == 'ci/actions' }}