compat: testing on dotnet 6 (#4473)

Author: bruno-garcia

src/platforms/dotnet/common/compatibility.mdx

@@ -24,6 +24,7 @@ If you're using an older version of .NET Framework or Mono, [our legacy SDK](/cl
 
 Sentry runs a validation test suite for SDK functionality in the following platforms:
 
+- .NET 6 - Windows, macOS, and Linux
 - .NET 5 - Windows, macOS, and Linux
 - .NET Core 3.1 - Windows, macOS, and Linux
 - .NET Core 2.1 - Windows, macOS, and Linux