Update build-and-test.yml

Author: JimBobSquarePants

.github/workflows/build-and-test.yml

@@ -48,7 +48,7 @@ jobs:
             - name: Setup DotNet SDK
               uses: actions/setup-dotnet@v1
               with:
-                  dotnet-version: "3.1.x"
+                  dotnet-version: [ "2.1.x", "3.1.x" ]
 
             - name: Install Azurite Linux
               if: matrix.options.os == 'ubuntu-latest'
@@ -108,7 +108,7 @@ jobs:
             - name: Setup DotNet SDK
               uses: actions/setup-dotnet@v1
               with:
-                  dotnet-version: "3.1.x"
+                  dotnet-version: [ "2.1.x", "3.1.x" ]
 
             - name: Pack
               shell: pwsh