static getOverallScores(lhr) {
    const cats = Object.keys(lhr.categories);
    const obj = {};
    for (const cat of cats) {
      obj[cat] = lhr.categories[cat].score * 100;
    }
    return obj;
  }
Returns the scores for each category.
@param {!Object} lhr Lighthouse results object.
@return {!Object<string, number>>}