Adds official .NET 5 support (#300)

.github/workflows/dotnet-core.yml

@@ -1,33 +0,0 @@
-name: Build
-
-on:
-  push:
-    branches: [ master ]
-  pull_request:
-    branches: [ master ]
-
-jobs:
-  build:
-    runs-on: ${{ matrix.os }}
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - os: macos-latest
-
-    steps:
-    - uses: actions/checkout@v2
-      with:
-        fetch-depth: 0 # avoid shallow clone so nbgv can do its work.
-    - name: Setup .NET Core
-      uses: actions/setup-dotnet@v1
-      with:
-        dotnet-version: 3.1.401
-    - name: Restore NuGet Packages
-      run: dotnet restore --force-evaluate
-    - name: Build Server
-      run: dotnet build -c Release -f netcoreapp3.1 --no-restore Projects/Server/Server.csproj
-    - name: Build UO Content
-      run: dotnet build -c Release -f netcoreapp3.1 --no-restore Projects/UOContent/UOContent.csproj
-    - name: Test
-      run: dotnet test --no-restore -f netcoreapp3.1