Add class to <h5>Parameters</h5> and other h5 elements

[hugolpz]

I would like to custom css for some large titles in order to reduce Chartjunk : "redundant pixels with no additional information".

To allows easier customisations via css, it would be better if we have something such as :

• <h5>Parameters:</h5> -> <h5 class="h5-parameters">Parameters:</h5>
• <h5>Returns:</h5> -> <h5 class="h5-returns">Returns</h5>

See also : https://github.com/clenemt/docdash/issues/19

[ar2rsawseen]

Added here: https://github.com/clenemt/docdash/commit/90f527fcc6906a166d103a228fe7e34c5e9b4640

[hugolpz]

@ar2rsawseen thank you ! that what was needed !