use .net 6 and 7 in ci

Author: kMutagene

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

@@ -17,7 +17,9 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@v1
       with:
-        dotnet-version: 6.x.x
+        dotnet-version: |
+            6.x.x
+            '7.0.103'
     - name: make script executable
       run: chmod u+x build.sh
     - name: Build and test