Recommend the curl command for potential WSL users on website

Rustup will provide the *nix focused curl command for windows users even in addition to recommending the Windows .exe file with a note that WSL users should use the command.

ghcup could do the same thing.

New users to the community might be confused by the recommendation to use Haskell Platform and not know that ghcup was not the same thing as what they were directed to install.