Interactive jupyter-inspect with prompt

[non-Jedi]

Would be great if there was a function hooking into the jupyter-inspect machinery that would prompt for a symbol and display the results for that symbol.

My vision for this is that you could also hook into the completion machinery and have an interface similar to describe-function/describe-variable but for Julia symbols.

I'll submit a PR if interest.

[nnicandro]

👍 for the PR. You could probably extract the completion table in jupyter-completion-at-point to get the symbols for completion. Also you may be able to re-use some of the code in jupyter-read-expression.