Add Giving Assistant to "donate options" page

https://www.torproject.org/donate/donate-options.html.en

Add Giving Assistant as an option after "Donate via Amazon Smile" following the same format:

Donate via Giving Assistant

Giving Assistant helps you donate a percentage of your cash back earnings to us with every purchase you make at 3,000+ popular online retailers.

Use Giving Assistant to save money and support the Tor Project