Improve the dev-install script

[jtpio]

The top-level package.json has a dev-install script here:

jupyter-chat/package.json

Line 36 in 025efd1

"dev-install": "lerna run dev-install --stream",

However the underlying packages don't seem to be exposing such script in their own package.json.

It could be useful to add such script in the different packages to speed up the dev install, which would for example run the jupyter labextension develop . --overwrite command for the lab extensions.

[brichet]

Thanks for pointing it out @jtpio