make passing reference to CSP.UseCspReportOnly, Explain CSP2 CSP3

[damienbod]

reported by snomad

Maybe make passing reference to CSP.UseCspReportOnly, super helpful on initial efforts into CSP. I am still lost on CSP level 2 and level 3 and just how much of a priority they should be. CanIUse shows CSP 1 at 94% globally, CSP2 at 80%. Not sure what to aim for.

Scott Helme
You can use CSP 2 and CSP 3 features and be backwards compatible. At a minimum I'd say CSP 2.