[DO NOT MERGE] Example: Custom environment

[ericfranz]

This shows how you could use a text area to provide a customizable environment setup prior to starting Jupyter notebook server.

Current limitations of the batch connect plugin prevent from modifying the size of the text area, so until that is fixed this may not be an ideal user experience, as the default text area is small. But some browsers do allow manually resizing, as I have done in this screenshot below:

[johrstrom]

Can this PR be closed? It seems it was never mean to be merged anyhow so it'll still exist as documentation.

Plus I'll add words like juypter text field and This would allow a user to set up their jupyter environment much more flexibly. They could even load the proper environments/modules for running other kernels available on the cluster, e.g. R, MATLAB. (quoted from the original request in discourse/mailing list).