Update VisualStudio.gitignore

Included Xamarin build files

VisualStudio.gitignore

@@ -32,6 +32,13 @@ bld/
 [Ll]og/
 [Ll]ogs/
 
+#Xamarin build results
+*/[Bb]in/
+*/[Oo]bj/
+*/[Oo]ut/
+*/[Ll]og/
+*/[Ll]ogs/
+
 # Visual Studio 2015/2017 cache/options directory
 .vs/
 # Uncomment if you have tasks that create the project's static files in wwwroot