Add Cross-Origin Policy feature with configurable headers (COEP, COOP, CORP)

[Spomky]

Hi,

This is a first attempt at addressing #371.
Feedback is very welcome.
Pease let me know if anything should be adjusted or improved.

EDIT: default values TBD.

Kind Regards,

[codecov-commenter]

Codecov Report

❌ Patch coverage is 96.22642% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.78%. Comparing base (7de9ce4) to head (3a14763).
⚠️ Report is 33 commits behind head on master.

Files with missing lines	Patch %	Lines
src/ContentSecurityPolicy/PolicyManager.php	0.00%	1 Missing ⚠️
src/EventListener/CrossOriginPolicyListener.php	90.90%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #372      +/-   ##
============================================
- Coverage     95.90%   95.78%   -0.13%     
- Complexity      443      469      +26     
============================================
  Files            53       58       +5     
  Lines          1979     2015      +36     
============================================
+ Hits           1898     1930      +32     
- Misses           81       85       +4     

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