Widget-code-input

This version is for JupyterLab 3.x.

This version include two new features from previous version:

* Support for both Jupyter notebook and JupyterLab.
* Support to select the code themes (eclipse, idea, material, midnight, monokai and solarized).

This new release has three new features:

* update the code themes description and add one more theme.
* upgrade it for Jupyter Lab 2.1.0.
* add the demos files.