code: function createIndex(addFn) {
    lunr.QueryLexer.termSeparator = lunr.tokenizer.separator = /\s+/;
    return lunr(/** @this */function() {
      this.ref('path');
      this.field('titleWords', {boost: 10});
      this.field('headingWords', {boost: 5});
      this.field('members', {boost: 4});
      this.field('keywords', {boost: 2});
      addFn(this);
    });
  }
docs: Create the lunr index - the docs should be an array of objects, each object containing the path and search terms for a page