build(aio): the the captured h1 as the title for the search index

If there is no title already provided, use the one captured from the renderedContent.

aio/tools/transforms/angular-base-package/index.js

@@ -55,6 +55,7 @@ module.exports = new Package('angular-base', [
 
     generateKeywordsProcessor.ignoreWordsFile = path.resolve(__dirname, 'ignore.words');
     generateKeywordsProcessor.docTypesToIgnore = ['example-region'];
+    generateKeywordsProcessor.propertiesToIgnore = ['renderedContent'];
   })
 
   // Where do we write the output files?