Add github workflow for buildsing (#14)

* Add github workflow for building

.github/workflows/build.yaml

@@ -0,0 +1,38 @@
+name: Build Firmware
+on: [push, pull_request]
+
+jobs:
+  build:
+    strategy:
+      matrix:
+        teensy: ['32', '40']
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - run: |
+        git fetch --prune --unshallow --tags
+        git describe --dirty --tags
+    - name: Set up Python
+      uses: actions/setup-python@v2
+    - name: Install PlatformIO
+      run: |
+        pip install platformio
+    - name: Build firmware
+      run: |
+        platformio run --environment teensy${{ matrix.teensy }}
+        cp .pio/build/teensy${{ matrix.teensy }}/firmware.hex firmware_teensy${{ matrix.teensy }}.hex
+    - name: Upload artifact
+      if: always()
+      uses: actions/upload-artifact@v3
+      with:
+        path: |
+          firmware_teensy${{ matrix.teenxy }}.hex
+    - name: Upload firmware to release
+      uses: svenstaro/upload-release-action@v2
+      with:
+        repo_token: ${{ secrets.GITHUB_TOKEN }}
+        file: ./firmware_teensy${{ matrix.teenxy }}.hex
+        tag: ${{ github.ref }}
+        overwrite: true
+        file_glob: true
+      if: startsWith(github.ref, 'refs/tags/')