Add .github directory with dependabot, sponsors, and pull request workflow.

Author: CodingFlow

.github/FUNDING.yml

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+github: CodingFlow

.github/dependabot.yml

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+version: 2
+updates:
+  - package-ecosystem: "nuget"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/pull-request.yml

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+name: pull-request-unit-tests
+run-name: Unit tests
+on: [push, workflow_dispatch]
+jobs:
+  build:
+    name: Unit tests
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        dotnet-version: ["10.0.x"]
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Setup .NET Core SDK ${{ matrix.dotnet-version }}
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: ${{ matrix.dotnet-version }}
+      - name: Install dependencies
+        run: dotnet restore
+      - name: Build
+        run: dotnet build --configuration Release --no-restore
+      - name: Test
+        run: dotnet test --no-restore --verbosity normal