Add basic GitHub Actions for Libretro Nintendo Switch

.github/workflows/libretro-switch.yml

@@ -0,0 +1,19 @@
+name: Libretro - Nintendo Switch CI
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    container: devkitpro/devkita64:latest
+
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+          submodules: recursive
+
+      - name: CMake
+        run: |
+          cmake -B build -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE=$DEVKITPRO/cmake/Switch.cmake -DLIBRETRO=ON
+          cmake --build build --config Release --parallel 2