Normalize keys taking in a platform aware way.
Normalize keys taking in a platform aware way.

Normalizing keys will return a list of shortcuts available for the
running platform (so platform specific keys + keys).  Process that
normalized list instead of the shortcut keys directly.

This means that winKeys, linuxKeys, and macKeys are properly supported
in jupyterlab shortcuts.

jupyter/jupyterlab,jupyter/jupyterlab,jupyter/jupyterlab,jupyter/jupyterlab,jupyter/jupyterlab