Document the mapping of system mouse cursors on Windows and Linux (#61399)
Document the mapping of system mouse cursors on Windows and Linux (#61399)

Add document for mouse cursor mapping on Windows and Linux.
tvolkert/flutter,cbracken/flutter,cbracken/flutter,flutter/flutter,flutter/flutter,tvolkert/flutter,Hixie/flutter,flutter/flutter,tvolkert/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,Hixie/flutter,cbracken/flutter,flutter/flutter,tvolkert/flutter,Hixie/flutter,tvolkert/flutter,tvolkert/flutter,flutter/flutter,cbracken/flutter,cbracken/flutter,flutter/flutter,Hixie/flutter,Hixie/flutter,Hixie/flutter,flutter/flutter,flutter/flutter,tvolkert/flutter,cbracken/flutter,Hixie/flutter,cbracken/flutter,cbracken/flutter,tvolkert/flutter,flutter/flutter,Hixie/flutter,tvolkert/flutter,cbracken/flutter,Hixie/flutter,flutter/flutter