Add explanation of naming convention

[ianhi]

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My understanding of the the widget naming convention is that the names are like so: Python: ipy<something> typescript: jupyter-<something>

With the idea being that the typescript part will be kernel-langauge agnostic and so shouldn't have an ipy in the name. i.e. if someone wanted make a cpp version of the widget they would only have to write cpp<something> they could then hook up to jupyter-<something> without ever having to write any typescript.

Conditional on the above being a correct assessment maybe this should be added to the top level readme of this repo?

Or in a more extreme move the cookiecutter could be changed to hint at this convention.