cmd: publish-to-catalog

[edeustace]

It'd be handy for the devs to be able to run a cmd to publish what they have so others can preview it. Right now you need to run the source to see it.

pie publish-to-catalog will pack the contents of docs/demo and deploy it to the catalog app.

• it'll clean any generated assets afterwards
• you can set the url to the publish endpoint (default: pie-catalog-demo.herokuapp.com)
• by default you can't overwrite a pkg@version, you can enable overwriting with --force
• catalog app should support multiple versions of the same package so one can see it's progress