Added GitHub actions

.github/workflows/linux-install.yml

+name: Linux Install and Test
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v2
+
+    - name: Run install-linux.sh
+      run: ./install-linux.sh
+
+    - name: Test Grapp executable
+      run: /opt/grapp/bin/Grapp --version
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