[Feature] LaTeX is generating... message on paste

[lucasvanmol]

On paste, display:

$$ \LaTeX \text{ is generating... } $$

$$
\LaTeX \text{ is generating... } \vphantom{image-id}
$$

• needs to handle failing cases (e.g. model not loaded or API unreachable)
• cases where $$block$$ formatting isn't used.
• cases where temp text gets moved.