Add Privacy Policy, and links to AkitaFeedback@gmail.com

[vezwork]

Part of #73

Adds a Privacy Policy as required by Privacy Policy & Secure Handling Requirements - Chrome Developers. The privacy policy addresses the following questions:

• What information does Akita collect?
• How does Akita use the information it collects?
• What information does Akita share? (none)
• How long does Akita retain your data?
• Which browser permissions does Akita use?
• Where can I find Akita's source code?

Additionally updates links and references to the Privacy Policy in README.md, CONTRIBUTING.md, and in the last tutorial slide in the extension popup.

Additionally adds contact links to our new email AkitaFeedback@gmail.com to README.md and CONTRIBUTING.md

This PR was co-authored by @sharon-wang .

[vezwork]

Thanks! Addressed your comments.