feat(convert): support color-related optional arguments for commands

[Shichien]

Fixes: #212, #206. This PR refactors the parsing and code generation logic for color-related commands in converter.rs and updates the corresponding definitions in standard.typ. It now provides full support for optional arguments such as [rgb], [RGB], [HTML], [cmyk], and [gray] color models for \color, \textcolor, and \colorbox.

For #206

#mi(`
\begin{tabular}{rrr}
  \toprule
  \textbf{Time} & \textbf{Velocity} & \textbf{Distance} \\
  \midrule
  5.0 & 5.0 & \color{blue}{12.5}\\
  20.0 & \textcolor{red}{20.0} & \textcolor{blue}{200.0} \\
  \bottomrule
\end{tabular}`,
)

Before	After

For #212

#import "@preview/mitex:0.2.6": *
#mitex(`\textbf{\textcolor{red}{A}}`)
#mitex(`\textcolor{red}{\textbf{A}}`)

Before	After

Features

For \color command

// Basic color name switch
#mitext(`{{\color{red} Red text } followed by normal text.}`)

// Different color models
#mitext(`{\color[rgb]{0.1, 0.7, 0.3} Green RGB text.}`)
#mitext(`{\color[HTML]{FF4500} Orange HTML text.}`)
#mitext(`{\color[cmyk]{1,0,1,0} Bright Green CMYK text.}`)
#mitext(`{\color[gray]{0.4} Dark Grey text.}`)

// Global color persistence across text and math
#mitext(`\color{magenta} Text and math $\alpha + \beta$ are both magenta.`)

// Nested color stack test
#mitext(`{\color{red} Red text {\color{blue} Blue text} back to Red.}`)

// Switching color inside math mode
#mitext(`$ x + {\color{red} y^2} + z $`)

// Consecutive declarations
#mitext(`\color{red} \color{blue} \color{green} Only Green should be visible.`)

// Edge case: Empty scope
#mitext(`{\color{red}}`)

After (Current PR)	LaTeX

For \textcolor command

• Note: As you can see, Mixed-mode color specifications (e.g., blue!50!green) are currently not supported. I plan to implement this in a future update.

#mitext(`
\textcolor{red}{Standard Red} \\
\textcolor[rgb]{0.1, 0.5, 0.8}{RGB Float Vector} \\
\textcolor[RGB]{20, 120, 200}{RGB Integer Vector} \\
\textcolor[HTML]{FF5733}{HTML Hex Caps} \\
\textcolor[HTML]{aacc00}{HTML Hex Lower} \\
\textcolor{blue!50!green}{Mixed Color Name (Fallback to map lookup)}
`)

#mitex(`
\textcolor{red}{
  \mathbf{
    \int_{
      \textcolor[rgb]{0,0,1}{
        \text{start \textcolor{orange}{$\infty$}}
      }
    }^{
      \textcolor{purple}{ \text{\textbf{end}} }
    }
    \textcolor[HTML]{008800}{x^2} \, dx
  }
} = \textcolor{cyan}{\mathfrak{Result}}
`)

#mitext(`
Normal
\textcolor [rgb] { 1, 0, 0 } { Spaced Args }
\textcolor
  [HTML]
  {0000FF}
  { Multi-line Args }
\textbf{\textcolor{red}{BoldRed}} vs \textcolor{red}{\textbf{RedBold}}
`)

#mitex(`
\sum_{\textcolor{red}{i}=0}^{\textcolor{blue}{\infty}} \frac{\textcolor[rgb]{0.9,0.1,0.1}{\sqrt{x^2+y^2}}}{\textcolor{green}{\overline{z}}}
+ \sqrt[\textcolor{purple}{3}]{\textcolor{orange}{8}}
`)

After (Current PR)	LaTeX

For \colorbox command

• Change \colorbox command align with the latex default value, see: Colored-boxes.
• Support optional arguments.
• Note: colorbox renders the boundary even if body is empty, which is consistent with the behavior of LaTeX.
• Note: In mitex v0.2.6, this only renders correctly inside #mitex().

// Base colorbox test
#mitext(`\colorbox{red}{Red Box}`)

// Different color models
#mitext(`\colorbox[rgb]{0.2, 0.8, 0.2}{Green RGB Box}`) // Error(mitex v0.2.6): Unknown symbol modifier

#mitext(`\colorbox[HTML]{445566}{Magenta HTML Box}`) // Error(mitex v0.2.6): Unknown symbol modifier

#mitext(`\colorbox[cmyk]{0,1,1,0}{Cyan Magenta Yellow Black Box}`) // Error(mitex v0.2.6): Unknown symbol modifier

#mitext(`\colorbox[gray]{0.5}{Grey Box}`) // Error(mitex v0.2.6): Unknown symbol modifier

// Nested colorboxes
#mitext(`\colorbox{black}{\color{white}White text in Black Box}`)

#mitext(`\colorbox{yellow}{\textcolor{red}{Red text in Yellow Box}}`)

// Math mode inside colorbox
#mitext(`\colorbox{cyan}{$E=mc^2$}`)

// Text mode inside colorbox
#mitext(`\colorbox{cyan}{\text{Text in Cyan Box}}`)

// Empty colorbox
#mitext(`\colorbox{red}{}`)

Before (mitex v0.2.6)	After (Current PR)	LaTeX

Warning

To preserve some of Typst's aesthetic, I set radius: 2pt, if this is deemed inconsistent with mitex's status as a LaTeX converter, please remove it.

[OrangeX4]

Sorry, I haven't had time to deal with mitex-related PRs before, thank you for your contribution