function getLineAndPreviousLine(lines, lineNumber) {
  return {
    line: lines.find(l => l.lineNumber === lineNumber),
    previousLine: lines.find(l => l.lineNumber === lineNumber - 1),
  };
}
@param {LH.Audit.Details.SnippetValue['lines']} lines
@param {number} lineNumber
@return {{line?: LH.Audit.Details.SnippetValue['lines'][0], previousLine?: LH.Audit.Details.SnippetValue['lines'][0]}}