add linear webhook example

[rushilpatel0]

Motivation

Content

Add an example to codegen-examples show how to use the linear.event decorator

Testing

Please check the following before marking your PR as ready for review

• I have added tests for my changes
• I have updated the documentation or added new documentation as needed

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

✅ All tests successful. No failed tests found.

Additional details and impacted files

[rushilpatel0]

I need to update the codegen dep version to 0.14.5 but having an issue with UV finding that version, pip install works though