bug#40900: Add face for function params in info

[ndame]

The Elisp info manual could be easier to read if parameters which are 
capitalized
could have a face too:

   If the minibuffer prompt string PROMPT does not end in ‘:’ ...


Though I don't know if it's possible to add language specific faces to info,
because a capitalized word could mean something else in an other language.

Maybe a face like Info-elisp-param-face which is added only if the current
info is about elisp?

Or simply generalizing it?  Info-capitalized-word-face?