## All PRs:

* [ ] Has tests
* [ ] Documentation updated

## Adding a new header

Generally, adding a new header is always OK.

* Is the header supported by any user agent? If so, which?
* What does it do?
* What are the valid values for the header?
* Where does the specification live?

## Adding a new CSP directive

* Is the directive supported by any user agent? If so, which?
* What does it do?
* What are the valid values for the directive?

