Feature Request: Tooltip for latex

Hi

Every time I develop documentation using notebook which I later convert to latex, I often need to look up for past labels to reference. For this I need to either double click the numbered equation every time and see the label or should right click and see its math jax.

Is it possible to provide a customized tool tip for at least display mode equations? I understand this could be borderline scope for jupyter, but Mathjax already offers tooltip as per link [here](http://www.onemathematicalcat.org/MathJaxDocumentation/toolTips.htm), but that is not working as its not recognized. Please let me know if any better workarounds available if this cannot be taken as FR.

The issue names no file, test, or entry point. First identify the notebook equation-rendering and MathJax integration points, then clarify the intended tooltip behavior for display-mode equations and how it should be validated.

Written by the indexing model from the issue text.