Allow docs search to search return / parameter / property types

[kav2k]

Currently, the search does not consider return type of methods, type of parameters or type of properties for the search. This can make it hard to see where types are used.

Example: trying to find how to get an instance of ClientUser.

https://discord.js.org/#/docs/main/stable/search?q=ClientUser
This will not consider Client#user as a search result.

It would be great to be able to find all methods/properties that use or return a particular type.