docs: add an installation guide

Add --shout to print the greeting in capitals

Use str.upper() so that accented names keep their accents.

cli: accept the name as a positional argument

`hello-hut Ada` reads better than `hello-hut --name Ada`.

Add greeting module and command-line entry point

hello-hut greets whoever is passed with --name, or "friend" by
default.

Initial commit