Feat/disable popping on backspace

[r-zane-spalding]

What does it do?

Adds disablePoppingOnBackspace prop to allow for optionally disabling the popping of nodes from the tree when the 'backspace' key is pressed in an empty search bar.

Fixes dowjones#550

Please mention in the format "Fixes #issueNumber" or "Closes #issueNumber".
This is important for semantic-release to correctly generate release tags and update issues.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

Checklist:

• [ x] I have performed a self-review of my own code
• [ x] I have commented my code, particularly in hard-to-understand areas
• [ x] Updated documentation (if applicable)
• [ x] Added tests that prove my fix is effective or that my feature works
• [ x] New and existing unit tests pass locally with my changes
• [ x] My changes generate no new warnings