Feature: preview equation on hover for referenced equations.

[branyang02]

Inspired by LaTeX Workshop, the goal is to dynamically display the referenced equation when hovered over a reference link in a notie page. The result should look like the following:

However, instead of hovering over an equation when editing, user should hover over a rendered reference link. For example, in the following notie render below,

When users hover over (1.11), notie should dynamically display the rendered equation D = E + F.

[branyang02]

Result here: