Added code to update CSP policy header based on custom site url

[AltamashShaikh]

Description:

Added code to update CSP policy header based on custom site url, Fixes: #59

Review

• [ ] Functional review done
• [ ] Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• [ ] Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• [ ] Security review done
• [ ] Wording review done
• [ ] Code review done
• [ ] Tests were added if useful/possible
• [ ] Reviewed for breaking changes
• [ ] Developer changelog updated if needed
• [ ] Documentation added if needed
• [ ] Existing documentation updated if needed

[tsteur]

Looks good to me @justinvelluppillai

Could check if a host was actually returned by parse_url($customSiteUrl, PHP_URL_HOST) but as we're checking that the configured url looks like a URL I suppose this should be always the case anyway.

[AltamashShaikh]

@tsteur Added check for host