Link to javascript-kernel (and/or xeus-javascript #3) in howto/configure/kernels

[westurner]

Problem

• The docs don't mention the JS kernel
• List of available JupyterLite kernels? jupyterlite#968

Suggested Improvement

• DOC: link to javascript-kernel (and/or xeus-javascript maybe add advanced features from xeus-javascript #3) in https://jupyterlite.readthedocs.io/en/latest/howto/configure/kernels.html and maybe also https://jupyterlite.readthedocs.io/en/latest/quickstart/using.html#kernels

[westurner]

https://jupyterlite.readthedocs.io/en/latest/howto/configure/kernels.html#jupyterlite-xeus :

jupyterlite-xeus
jupyterlite-xeus is a loader package to enable Xeus-based kernels in JupyterLite.