add `curl` to the one line `linux` installer via `brave.com`

If possible, we should add installing `curl` to the one line install script for `Linux` that's on `brave.com`. For example, a new user that just installed `Ubuntu` and wants to grab Brave right away will run into the following:

CCing @wknapik @fmarier @mihaiplesa

Start by locating the one-line Linux installer published on brave.com in this install.sh repository and inspect how package prerequisites are installed. Add curl to that installation flow, then verify that a fresh Ubuntu setup can run the installer successfully with curl available.

Written by the indexing model from the issue text.