Added GitHub Actions workflow

.github/workflows/build.yml

@@ -0,0 +1,33 @@
+name: Build Executable
+
+on: [push]
+
+jobs:
+  build:
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+
+    runs-on: ${{ matrix.os }}
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python
+      uses: actions/setup-python@v2
+      with:
+        python-version: '3.x'
+
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install pyinstaller
+
+    - name: Build with PyInstaller
+      run: |
+        pyinstaller --onefile --windowed SortingApp.py
+
+    - name: Upload executable
+      uses: actions/upload-artifact@v2
+      with:
+        name: executable
+        path: dist/*