resizing figures in webagg

[eyurtsev]

The webagg resizing does not work well because mouse events are not ignored during the resize. I implemented a fix for this locally. The changes are outlined below.

I also included some cosmetic changes to make resizing a bit prettier.

https://github.com/eyurtsev/matplotlib/compare/fix_webagg_resize

If you're happy with the changes, I can do a PR.

[tacaswell]

A PR is always welcome

[pelson]

Thanks for the PR @eyurtsev. I'll close this issue.