function withHeadingContext(relativeHeadingLevel, markdown) {
  return markdown.replaceAll(/^(#+)/gm, (match, markdownHeadingTokens) => {
    return "#".repeat(markdownHeadingTokens.length + relativeHeadingLevel);
  });
}
Adjusts the headings in the given `markdown` to be in a given heading context.
Headings must start in a line.
Preceding whitespace or any other character will result in the heading not being recognized.

@example `withHeadingContext(2, '# Heading') === '### Heading'`
@param {number} relativeHeadingLevel
@param {string} markdown