CRWA: --yes

[Tobbe]

A lot of CLIs accept a --yes or -y flag to accept all defaults.

Some examples includes: yarn init -y, npm init -y, apt-get -y install <package>

There's even a unix command that tries to do this for commands that don't support that flag. It's called yes https://linux.die.net/man/1/yes

But, as the wikipedia page for yes says:

This usage may be obsolete today, as most commands that would request response from the user have either a 'force' option (e.g., rm -f) or an 'assume-yes' option (for example, apt -y)

I think we should support -y for create-redwood-app. This PR adds that.

EDIT:
Additional note: You can still override a specific setting. Like yarn create redwood-app --no-git-init --yes to not initialize a git repo

[jtoar]

Works great for me, and the idea seems sensible, especially for us for testing, though it's certainly useful for users too