feat: use Bridgetown CLI directly instead of Yarn

[jaredcwhite]

I put a question mark at the end there because I'm not entirely sold on the idea myself, but I've been musing on the idea of making the bridgetown command itself handle the common use cases we're currently relying on yarn to do. Think:

• bridgetown start (or dev)
• bridgetown deploy
• bridgetown frontend:compile
• etc.

I also did a personal hackathon a couple of days ago to try out Rake/Roda and in the processes essentially recreated Concurrently/Foreman/etc. in order to run multiple processes in parallel from a single Ruby script (Bridgetown watch, Webpack, and Browsersync). I like the idea of removing dependencies there and handling all the processes directly. It's true yarn has a lot of institutional awareness already and it's easy to tweak and add your own scripts in package.json. On the other hand…we're a Ruby tool, so why are using Yarn instead of Rake?

[jaredcwhite]

Earlier today prototyped bridgetown handling Rakefile tasks just like how rails does these days, and it's pretty nifty…thinking it might be the right call to move in that direction.

[jaredcwhite]

bin/bridgetown start etc. has been merged into v1.0 alpha. Closing.