add a `--list` option to display known available types/archetypes

[isao]

something like:

% mojito create --list
app
mojit
mything
thatstuff

% mojito create app --list
default
full
simple

% mojito create mything/configs --list
app.yaml
defaults.json
foo.bar.js

[drewfish]

🏃

[mridgway]

Is running man the new ship it? I approve of this (the running man, I haven't looked at the codes).

[drewfish]

I was trying to express "I like, let's run with the idea".

[isao]

output of --list could also be used in custom shell completions