create github actions workflow

* does automatic builds on push
* creates releases from git tags
* uploads release builds to new releases

.github/workflows/dotnet.yml

@@ -0,0 +1,52 @@
+name: .NET Build
+on: [push]
+
+jobs:
+  build:
+    runs-on: windows-latest
+    steps:
+    - uses: actions/checkout@v1
+    # Set Path workaround for https://github.com/actions/virtual-environments/issues/263
+    - name: "Temp step to Set Path for Windows"
+      run: |
+        echo "::add-path::C:\Program Files\Git\mingw64\bin"
+        echo "::add-path::C:\Program Files\Git\usr\bin"
+        echo "::add-path::C:\Program Files\Git\bin"
+    - name: Setup MSBuild
+      uses: warrenbuckley/Setup-MSBuild@v1
+    - name: Install dependencies
+      run: msbuild -t:restore
+    - name: Build project
+      run: msbuild ModAssistant/ModAssistant.csproj /t:Build /p:Configuration=Release
+    - name: Cleanup release
+      shell: bash
+      run: |
+        find "ModAssistant/bin/Release" -type f ! -name "ModAssistant.exe" -delete
+        cp "LICENSE" "ModAssistant/bin/Release/LICENSE.ModAssistant.txt"
+    - name: Upload Build
+      if: contains(github.ref, 'refs/tags/') == false
+      uses: actions/upload-artifact@v1
+      with:
+        name: ModAssistant-${{ github.sha }}
+        path: ./ModAssistant/bin/Release
+    - name: Create Release
+      if: contains(github.ref, 'refs/tags/') == true
+      id: create_release
+      uses: actions/create-release@v1.0.0
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      with:
+        tag_name: ${{ github.ref }}
+        release_name: Mod Assistant ${{ github.ref }}
+        draft: false
+        prerelease: false
+    - name: Upload Release Asset
+      if: contains(github.ref, 'refs/tags/') == true
+      uses: actions/upload-release-asset@v1.0.1
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      with:
+        upload_url: ${{ steps.create_release.outputs.upload_url }}
+        asset_path: ./ModAssistant/bin/Release/ModAssistant.exe
+        asset_name: ModAssistant.exe
+        asset_content_type: application/vnd.microsoft.portable-executable