pm-enhance dragging experience

[dnenov]

Purpose

A small PR to enhance the dragging interaction for the Package Manager window. Previously only a narrow zone around the Title name would allow dragging, now the whole title bar allows that interaction.

Declarations

Check these if you believe they are true

• The codebase is in a better state after this PR
• Is documented according to the standards
• The level of testing this PR includes is appropriate
• User facing strings, if any, are extracted into *.resx files
• All tests pass using the self-service CI.
• Snapshot of UI changes, if any.
• Changes to the API follow Semantic Versioning and are documented in the API Changes document.
• This PR modifies some build requirements and the readme is updated
• This PR contains no files larger than 50 MB

Release Notes

• created an invisible border to occupy the title bar to help with dragging experience

Reviewers

@reddyashish
@QilongTang

FYIs

@mjkkirschner

[reddyashish]

https://master-15.jenkins.autodesk.com/view/DYN/job/DYN-DevCI_Self_Service/1332/

[reddyashish]

CI passed.