chore: added TypeScript Typing for match variable

[mdqst]

updated the code to properly type the match variable in two places:

• In the findAnchorsInFile function (for matching headers in the file).
• In the checkLinks function (for matching links in the Markdown file).

this ensures TypeScript correctly handles the match variable as either a RegExpExecArray (when there are matches) or null (when no matches are found).