Update DrHeader according to OWASP Secure Headers Project

[manuel-sommer]

• drHEADer version: 1.5.3
• Python version: 3.8.10
• Operating System: Linux

This Project should be updated according to the best practice reommendations of the OWASP Secure Headers Project https://owasp.org/www-project-secure-headers/

Multiple Headers suggested in the OWASP Secure Headers Project are not scanned with DrHeader (e.g. Cross-Origin-Opener-Policy).

Furthermore, we should merge development into master (Last release was Nov 2, 2020) to apply the deprecated X-XSS header #137.

[dpauk]

Thanks @manuel-sommer. We're going to be publishing a refactor of some of the code in the next few weeks and will look at your recommendations after that.

[manuel-sommer]

@dpauk , you can review the PR or take it as a starting point.