[Rd] Offer zip builds

[Steven Penny]

If you go here:

https://cran.cnr.berkeley.edu/bin/windows/base

you see EXE installers for Windows. This contrasts with other programming
languages that offer both an executable installer and ZIP files that can be
extracted and run. For example Go:

https://golang.org/dl

and Nim:

https://nim-lang.org/install_windows.html

Python:

https://python.org/downloads/release/python-373

and C#:

https://dotnet.microsoft.com/download/dotnet-core/2.2

PHP:

https://windows.php.net/download

Perl:

http://strawberryperl.com/releases.html