code: function getChangelogSectionIndex (lines) {
    const validSectionHeaders = [
      '#changelog',
      '# changelog'
    ]
  
    let index = -1
    for (let i = 0; i < lines.length; i++) {
      const processedLine = lines[i].trim().toLowerCase()
      if (validSectionHeaders.indexOf(processedLine) !== -1) {
        if (index !== -1) {
          throw new Error(`Multiple changelog sections found. Line ${index + 1} and line ${i + 1}.`)
        }
        index = i
      }
    }
  
    return index
  }
docs: Given a PR description, find the index of the # CHANGELOG section
  @param {String[]} lines - lines in the pr description
  @returns {Number} the index of the # CHANGELOG section (or -1)
  @throws Error if there is more than one matching line