add supported versions

Author: mayuanyang

.github/workflows/ci.yml

@@ -12,13 +12,15 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Setup .NET Core 3.1
-        uses: actions/setup-dotnet@v2
+        uses: actions/setup-dotnet@v3
         with:
           dotnet-version: |
             3.1.x
             5.0.x
             6.0.x
             7.0.x
+            8.0.x
+            9.0.x
       - name: Install dependencies
         run: dotnet restore Mediator.Net.sln
       - name: Build