feat: add support for \smash command

[Shichien]

Support \smash Command

It was noted in #43 that the \smash command is included in the roadmap. But the current version triggers:
error: unknown command: \smash.

this PR provides a basic implementation.

• Note: Optional arguments [t] and [b] are currently not supported.
• The command renders the content as a math formula using $#it$ by default.

Typst Preview

#table(
  columns: (1.5fr, 2fr, 2fr),
  inset: 8pt,
  align: horizon + center,
  table.header([Scenario], [Unbalanced], [Smashed]),

  [Square Root],
  [#mi(`$\sqrt{x} + \sqrt{y} + \sqrt{T} + \sqrt{\sum}$`)],
  [#mi(`$\sqrt{\smash{x}} + \sqrt{\smash{y}} + \sqrt{\smash{T}} + \sqrt{\smash{\sum}}$`)],

  [Underline Alignment],
  [#mi(`$\underline{x} + \underline{y} + \underline{a}$`)],
  [#mi(`$\underline{\smash{x}} + \underline{\smash{y}} + \underline{\smash{a}}$`)],

  [Line Height Protection],
  [Text #mi(`$A_{2_2^{2^2}}$`) expands line height],
  [Text #mi(`$A_{\smash{2_2^{2^2}}}$`) maintains line height],

  [Compact Overline],
  [#mi(`$\overline{\frac{1}{2}}$`)],
  [#mi(`$\overline{\smash{\frac{1}{2}}}$`)],

  [Compact Underline],
  [#mi(`$\underline{\frac{1}{2}}$`)],
  [#mi(`$\underline{\smash{\frac{1}{2}}}$`)],
)

LaTeX Preview

\begin{table}[h]
    \centering
    \Large
    \renewcommand{\arraystretch}{1.8}
    \begin{tabularx}{\textwidth}{|>{\centering\arraybackslash}m{5cm}|>{\centering\arraybackslash}X|>{\centering\arraybackslash}X|}
        \hline
        \textbf{Scenario}      & \textbf{Unbalanced}                             & \textbf{Smashed}                                                               \\
        \hline
        Square Root            & $\sqrt{x} + \sqrt{y} + \sqrt{T} + \sqrt{\sum}$  & $\sqrt{\smash{x}} + \sqrt{\smash{y}} + \sqrt{\smash{T}} + \sqrt{\smash{\sum}}$ \\
        \hline
        Underline Alignment    & $\underline{x} + \underline{y} + \underline{a}$ & $\underline{\smash{x}} + \underline{\smash{y}} + \underline{\smash{a}}$        \\
        \hline
        Line Height Protection & Text $A_{2_2^{2^2}}$ expands line height        & Text $A_{\smash{2_2^{2^2}}}$ maintains line height                             \\
        \hline
        Compact Overline       & $\overline{\frac{1}{2}}$                        & $\overline{\smash{\frac{1}{2}}}$                                               \\
        \hline
        Compact Underline      & $\underline{\frac{1}{2}}$                       & $\underline{\smash{\frac{1}{2}}}$                                              \\
        \hline
    \end{tabularx}
\end{table}

[OrangeX4]

Thanks!