search friendly html document by removing <span>s

[arbipher]

It may be the case for non-expert users to search for a type to check whether some standard function exist,
e.g. I searched 'a -> 'a -> 'a in the List module to check how many variants of List.reduce and pick one.

However, the current generated HTML doesn't support a naive search of type string like 'a -> 'a -> 'a. The reason is there are some <span> in it to prevent web browser in page search to find it easilly.

<span>(<span class="type-var">'a</span> <span>-&gt;</span> <span class="type-var">'a</span> <span>-&gt;</span> <span class="type-var">'a</span>)</span>

I can search 'a -> 'a -> 'a in the source code.

I suggest removing some spans in the output to make it friendly to naive in-page search.

[lpw25]

The problem seems to be related to our css rather than the spans themselves. Our internal docs site uses different css and doesn't suffer from this problem. We're intending to switch our external documentation to the same css as our internal site at our next release, so this should be resolved when that happens.