Added optional props argument to Lasso Widget __init__ to customize Lasso line

[kbturk]

PR summary

Added an optional props argument to the Lasso Widget init to allow customization of the Lasso line and a test to check the new code. This is similar to the LassoSelector optional props argument and props must be properties in Line2D.

PR checklist

• [N/A] "closes #0000" is in the body of the PR description to link the related issue
• new and changed code is tested
• [N/A*] Plotting related features are demonstrated in an example
• [N/A] New Features and API Changes are noted with a directive and release note
• Documentation complies with general and docstring guidelines

*There is a tutorial for the Lasso Widget but since this is an optional argument it doesn't need to be updated.

[github-actions]

Thank you for opening your first PR into Matplotlib!

If you have not heard from us in a week or so, please leave a new comment below and that should bring it to our attention. Most of our reviewers are volunteers and sometimes things fall through the cracks.

You can also join us on gitter for real-time discussion.

For details on testing, writing docs, and our review process, please see the developer guide

We strive to be a welcoming and open project. Please follow our Code of Conduct.

[oscargus]

Thanks for your contribution! Some comments to get the doc builds to pass and have a slightly more expected interface. The idea is good for sure!

[oscargus]

Thanks!

For whoever merges this: please squash upon merge.

[QuLogic]

It looks like there are some conflicts here; are you able to rebase this PR?

[timhoffm]

I've fix the conflict (expired kw-only deprecation vs. Modified signature).

Please squash-merge.

[timhoffm]

Thank you for your work @kbturk and congratulations on your first merged Matplotlib PR 🎉

I hope we hear from you again.

[kbturk]

Thank you @timhoffm @QuLogic @oscargus for all the help!