Added GitHub Actions config

.github/workflows/build.yaml

@@ -0,0 +1,18 @@
+name: Build
+on: [push]
+
+jobs:
+  build:
+    name: NickelMenu
+    runs-on: ubuntu-latest
+    container: docker.io/geek1011/kobo-toolchain:latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v1
+    - name: Build
+      run: make all koboroot
+    - name: Upload
+      uses: actions/upload-artifact@v1
+      with:
+        name: NickelMenu
+        path: KoboRoot.tgz