Generate search index entries for all headings, not just H1 and H2 #644
Currently search index generation is limited to H1 and H2, which is hard-coded. I have found it necessary to extend this to H3 and H4, as I wanted to provide more specific search results. Not sure what a good balance would be (e.g. stop at H4), as the level of headings included in the TOC, for example, is up to the template, so I opted for no limits.