Report unsupported macros by katex and expand user-define commands

* Break Up LaTeX Source on Section Macros (#101)

Break up a latex source by divisions (`\section` , `\subsection`, etc.) and turn those divisions into environments. E.g., `\section{foo}XXX\section{bar}YYY` becomes 

```
\begin{_section}[foo]XXX\end{_section}
\begin{_section}[bar]YYY\end{_section}
```

This is an intermediate step in the PreTeXt conversion.

* [WIP] author-info (#100)

Add function to extract information from the `\author{...}` tag that appears before `\begin{document}...`

* Fix the skipped test cases in the PreTeXt package (#103)

Necessary macro subs and environment subs to create valid PreTeXt from LaTeX.

* Added LaTeX to PreTeXt Plugin to the CLI package (#113)

* started adding pretext package to cli

* Upgrade deps

* Rebuild documentation

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Co-authored-by: Renee <[email protected]>
Co-authored-by: Bo-Y-G <[email protected]>