Add Twilio HTTP headers article to the Web Security lesson

[MichelleGlauser]

"HTTP Headers for the Responsible Developer" is a great resource we should share in an applicable topic: https://www.twilio.com/blog/a-http-headers-for-the-responsible-developer

Target file to add: https://github.com/Techtonica/curriculum/blob/master/security/web-security.md

[vegetabill]

Target: https://github.com/Techtonica/curriculum/blob/master/security/web-security.md

[Tahanima]

Hello, I am a GSSoC20 participant and I want to contribute to this issue.

[habeeba-naaz]

I am gssoc20 participant...interested to work on this...if possible please assign?

[CipherGirl]

Hello, I'm GSSoC 20 participant. I would like to work in this issue. If it's available can you please assign to me?

[vegetabill]

I am assigning this to @Tahanima

Thanks for volunteering to help Techtonica improve its curriculum!

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[Tahanima]

Thank You @vegetabill for assigning me to this issue. Yes, I am still interested in this issue.

[vegetabill]

Closing this. I added it to the scoresheet.