Add CSP security with Helmet.js

[tristanMatthias]

I'm submitting a ...

• feature request

For project (Choose one)

• @origami/core-lib

What is the current behavior?
There is currently no protection with CSP (Content Security Policy). This should be enabled to provide further protection.

What is the expected behavior?
A good default setting, with the option to override from the Origami file

What is the motivation / use case for changing the behavior?
Better security

Please tell us about your environment:
Any Origami project