[feature] Add two features to this library: remove KaTeX and FrontMatter.

[PrinOrange]

• First is to remove KaTeX. Because KaTeX contains a large number of special symbols, these codes are difficult to parse after extracting them into plain text. It can specify whether to remove KaTeX through Options.preserveKaTeX?: boolean;
• Second, remove frontmatter for markdown. frontmatter is the header metadata and its markup in markdown. It is generally recognized by other programs and has nothing to do with the text content. So this part can be removed.
• Finally, format the code using Prettier and upgrade some outdated dependencies.