Add management of COOP/COEP headers

[TristanPouliquen]

Hello,

We've come across the need to define COOP/COEP headers in our Symfony application.

As of today, this is not handled by this bundle sadly, so we had to set it up manually.

As this seems really similar to CSP header setup, would it be interesting for the bundle to handle this usecase too?

Main feature points:

• Define default COOP/COEP policy
• Define pattern-restricted COOP/COEP policies (in the same way as nelmio cors bundle)
• Configure report-only mode
  • Define report groups
  • Define the Reporting Endpoints configuration

[Seldaek]

See #372 - nobody has gotten to review it yet tho. If you wanna take a look and/or try it out and give feedback that'd be great.