Remove appveyor.yml, add build.yml for GitHub

Author: axunonb

.github/workflows/build.yml

@@ -0,0 +1,62 @@
+name: Build and Test
+
+on:
+  push:
+    branches:
+      - main
+      - 'pr/**'
+    paths-ignore:
+      - '**/*.md'
+  pull_request:
+    branches:
+      - main
+    paths-ignore:
+      - '**/*.md'
+
+env:
+  DOTNET_SKIP_FIRST_TIME_EXPERIENCE: true
+  DOTNET_CLI_TELEMETRY_OPTOUT: 1
+  DOTNET_NOLOGO: true
+  VERSION: '5.13.0'
+
+jobs:
+
+  build-linux:
+    name: Build and Test (Linux)
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: Src
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v6
+      
+    - name: Setup .NET
+      uses: actions/setup-dotnet@v5
+      with:
+        dotnet-version: |
+          10.0.x
+
+    - name: Display .NET version
+      run: dotnet --version
+
+    - name: Restore dependencies
+      run: dotnet restore --verbosity quiet
+
+    - name: Add AltCover package
+      run: dotnet add ./MailMergeLib.Tests/MailMergeLib.Tests.csproj package AltCover
+
+    - name: Build solution
+      run: dotnet build MailMergeLib.sln /verbosity:minimal /t:rebuild /p:configuration=release /nowarn:CS1591,CS0618
+
+    - name: Run tests
+      run: dotnet test --framework net10.0 --no-build --configuration release MailMergeLib.sln /p:AltCover=true /p:AltCoverXmlReport="coverage.xml" /p:AltCoverStrongNameKey="../MailMergeLib/MailMergeLib.snk" /p:AltCoverAssemblyExcludeFilter="MailMergeLib.Tests|NUnit3.TestAdapter" /p:AltCoverLineCover="true"
+      
+    - name: Upload coverage to Codecov
+      uses: codecov/codecov-action@v5
+      with:
+        files: ./MailMergeLib.Tests/coverage.net10.0.xml
+        flags: net10.0-linux
+        name: net10.0-linux
+        token: ${{ secrets.CODECOV_TOKEN }}