Add Content Security Policy builder

[cak]

• Enhance the configuration of the Content Security Policy header
• Add CSP Keywords
• Add Report-To Directive

let cspConfig = ContentSecurityPolicy()
        .defaultSrc(sources: CSPKeywords.none)
        .scriptSrc(sources: "https://static.brokenhands.io")
        .styleSrc(sources: "https://static.brokenhands.io")
        .imgSrc(sources: "https://static.brokenhands.io")
        .fontSrc(sources: "https://static.brokenhands.io")
        .connectSrc(sources: "https://*.brokenhands.io")
        .formAction(sources: CSPKeywords.`self`)
        .upgradeInsecureRequests()
        .blockAllMixedContent()
        .requireSriFor(values: "script", "style")
        .reportUri(uri: "https://csp-report.brokenhands.io")
        
let securityHeaders = SecurityHeaders(contentSecurityPolicyConfiguration: cspConfig)

Content-Security-Policy: default-src 'none'; script-src https://static.brokenhands.io; style-src https://static.brokenhands.io; img-src https://static.brokenhands.io; font-src https://static.brokenhands.io; connect-src https://*.brokenhands.io; form-action 'self'; upgrade-insecure-requests; block-all-mixed-content; require-sri-for script style; report-uri https://csp-report.brokenhands.io

[0xTim]

Looks awesome! Few minor changes

[codecov]

Codecov Report

Merging #14 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master    #14   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          10     10           
  Lines         130    218   +88     
=====================================
+ Hits          130    218   +88

Impacted Files	Coverage Δ
Sources/VaporSecurityHeaders/SecurityHeaders.swift	100% <ø> (ø)	⬆️
...gurations/ContentSecurityPolicyConfiguration.swift	100% <100%> (ø)	⬆️
.../VaporSecurityHeaders/SecurityHeadersFactory.swift	100% <100%> (ø)	⬆️

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