This is my attempt for adding support for stylus on windows.
It's work in progress! I post it here to indicate that I'm working on it and that the same work is not done twice

I'm working on the flutter_window.cpp file. Maybe I need to touch some other code to allow additional information like pressure, rotation and more.

Would fix #102836 and #65248

There should be no breaking change other than stylus would be reported as stylus instead of touch.

Tested with flutter master on my test project:

https://github.com/CodeDoctorDE/flutter-input-demo

Tests are currently not there, I will add them next.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• I followed the breaking change policy and added Data Driven Fixes where supported.
• All existing and new tests are passing.

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