Tags in documentation comments are not indexed

[art-w]

When searching in documentation comments, some words appear to not be indexed. For example Stdlib.Array.get disappears once we add the words from the second line of its documentation to the query (invalid argument, negative, outside..)

I suspect this line in odoc.search is responsible for ignoring @raise ... sections of the comment : https://github.com/ocaml/odoc/blob/master/src/search/text.ml#L53 (since we index the text rendering and not the html one)