Adds ui-lib

[necoline]

I'm not sure if this should be a standalone option or part of the parcel branch. I think it depends on the extent to which we want to maintain these (parcel and browserify) branches as 'minimal config templates'.

I have had a few requests in the past for a ui-lib app template and I thought this would be an ideal way to offer a no-fuss application spin-up for folks on other teams when they need to create very simple interfaces

[AliceR]

That seems very specific. Is there a reason for it?

[AliceR]

Nice addition!! 🚀

Things I noticed, which apply to all the cookiecutter branches:

• we should rename the default branch that is created. Currently master, I'd suggest develop
• Maybe we should run yarn install after initialization (add step in post_gen_project.py)?
• I got this warning:

@parcel/transformer-babel: It looks like you're using a JavaScript Babel config file. This means the config cannot be watched for changes, and Babel transformations cannot be cached. You'll need to restart Parcel for changes to this config to take effect. Try using a babel.config.json file instead.

• the mapbox token is missing initially. I wonder how we can improve the dev experience around that, just a blank screen does not help (the console gives a clue though). Ask for the token in cli when creating the project?