[Feature Request] Add a short option for --content-disposition

[No-Reply-Wolfietech via Primary discussion list for GNU Wget]

Nowadays it seems increasingly common to find a file that is not being hosted 
where its actually stored, for access control presumably, and it seems to make 
no sense in having to type content-disposition when a single letter flag is all 
that is needed?

Sent with [Proton Mail](https://proton.me/) secure email.