[DEL] - JupyterLab should be navigable by keyboard alone.

[trallard]

The purpose of this WP is to move towards making JLab navigable through a keyboard.

This includes tasks such as #134

### Related issues and tasks
- [ ] #168 
- [ ] #167 
- [ ] #169 
- [ ] #134 
- [ ] https://github.com/Quansight-Labs/jupyter-a11y-mgmt/issues/182