Added 'SentryUploadAndroidProguardMapping' to MSBuild properties (#7476)

Author: bitsandfoxes

src/platforms/dotnet/common/configuration/msbuild.mdx

@@ -108,6 +108,9 @@ if you only want these features enabled in a GitHub Actions CI workflow, you cou
   <!-- Sends sources to Sentry, enabling display of source context. -->
   <SentryUploadSources>true</SentryUploadSources>
 
+  <!-- If you are targeting Android, sends proguard mapping file to Sentry. -->
+  <SentryUploadAndroidProguardMapping>true</SentryUploadAndroidProguardMapping>
+
 </PropertyGroup>
 
 ```