Add NuGet metadata to library and add two new workflows for master pull requests and releases on github

.github/workflows/release-nuget.yml

@@ -0,0 +1,30 @@
+on:
+  release:
+    types: [published]
+
+jobs:
+  release-nuget:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: 8.0.x
+      - name: Restore dependencies
+        run: dotnet restore src/DotTiled.sln
+      - name: Build
+        run: dotnet build --no-restore src/DotTiled.sln
+      - name: Test
+        run: dotnet test --no-build --verbosity normal src/DotTiled.sln
+      - name: Lint style
+        run: dotnet format style --verify-no-changes --verbosity diagnostic src/DotTiled.sln
+      - name: Lint analyzers
+        run: dotnet format analyzers --verify-no-changes --verbosity diagnostic src/DotTiled.sln
+      - name: Pack
+        run: make pack
+      - name: Publish to NuGet.org
+        run: |
+          dotnet nuget push ./nupkg/*.nupkg -k ${{ secrets.NUGET_API_KEY }} -s https://api.nuget.org/v3/index.json --skip-duplicate
+          dotnet nuget push ./nupkg/*.snupkg -k ${{ secrets.NUGET_API_KEY }} -s https://api.nuget.org/v3/index.json --skip-duplicate