code: function walkCollections(patterns, drizzleData, currentKey = 'patterns') {
    for (const patternKey in patterns) {
      if (patternKey === 'collection') {
        renderCollection(patterns, drizzleData, currentKey);
      } else {
        walkCollections(patterns[patternKey], drizzleData, patternKey);
      }
    }
    return drizzleData.patterns;
  }
docs: Recursively walk through the patterns data object and render content
  for "pattern collections" (any entry in `patterns` that contains an
  `items` property).
  
  @param {Object} patterns     The current level of the `patterns` object.
  @param {Object} drizzleData
  @param {String} currentKey   The key for the current `patterns` object.
  @return {Object} drizzleData All drizzleData