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

.github/workflows/master-pr.yml

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+on:
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  check-pr-version:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout PR branch
+        uses: actions/checkout@v3
+        
+      - name: Get version from PR branch
+        id: pr_version
+        run: |
+          PR_VERSION=$(grep '<Version>' **/*.csproj | sed -E 's/.*<Version>(.*)<\/Version>.*/\1/')
+          echo "PR_VERSION=$PR_VERSION" >> $GITHUB_ENV
+
+      - name: Checkout master branch
+        run: |
+          git fetch origin master
+          git checkout origin/master
+
+      - name: Get version from master branch
+        id: master_version
+        run: |
+          MASTER_VERSION=$(grep '<Version>' **/*.csproj | sed -E 's/.*<Version>(.*)<\/Version>.*/\1/')
+          echo "MASTER_VERSION=$MASTER_VERSION" >> $GITHUB_ENV
+
+      - name: Compare versions
+        run: |
+          if [ "$(printf '%s\n' "$PR_VERSION" "$MASTER_VERSION" | sort -V | head -n1)" = "$PR_VERSION" ] && [ "$PR_VERSION" != "$MASTER_VERSION" ]; then
+            echo "Version in PR is not higher than master."
+            exit 1
+          else
+            echo "Version in PR is higher than master."
+          fi

.github/workflows/release-nuget.yml

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+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