Update devcontainer.json

Author: MeenaAlfons

.devcontainer/devcontainer.json

@@ -1,5 +1,5 @@
 {
-  "image": "mcr.microsoft.com/vscode/devcontainers/dotnet:3.1",
+  "image": "mcr.microsoft.com/vscode/devcontainers/dotnet:5.0",
   "features": {
   }
 }