(For details, please refer to the GDoc link in the Epic description)

Difficulty: easy
Skill requirement: JavaScript (basic), Jelly (basic)

Move the script tag BuildTimelineWidget/control.jelly#L40-L167 to its own file.

To inject separate file into Jelly, you can use <st:adjunct includes=...
One variable injected, you will need to use advice from https://www.jenkins.io/doc/developer/security/xss-prevention/#passing-values-to-javascript