Close tabs on middle click

[dcdenu4]

Description

Prevent the default behavior of a middle click opening a new window / tab on an InVEST Tab and instead close that tab.

I was unsure of whether this should live on the Nav.Link element or up one on the Nav.Item element. I opted for Nav.Link because the default nature of middle click on links...

I was unsure of whether this deserved a test? I could not find a "close tab" / "switch tab" test in investtabtest

Manually verified behavior on Windows with mouse wheel middle click in development build.

Fixes #1261

Checklist

• Updated HISTORY.rst and link to any relevant issue (if these changes are user-facing)
• [ ] Updated the user's guide (if needed)
• Tested the affected models' UIs (if relevant)

[davemfish]

Looks good to me! I don't think this requires testing. But FYI the tests that open and close tabs are in app.test.js.

And I think it makes sense to place this handler on the Nav.Link, not the Nav.Item.