Improve styling of notebook toolbar.
Improve styling of notebook toolbar.

eskirk/jupyterlab,jupyter/jupyterlab,jupyter/jupyterlab,jupyter/jupyterlab,eskirk/jupyterlab,eskirk/jupyterlab,jupyter/jupyterlab,eskirk/jupyterlab,charnpreetsingh185/jupyterlab,eskirk/jupyterlab,charnpreetsingh185/jupyterlab,charnpreetsingh185/jupyterlab,charnpreetsingh185/jupyterlab,charnpreetsingh185/jupyterlab,jupyter/jupyterlab