Work on support.torproject.org usabilty issues based on user feedback

From sponsor 9's phase 5 trainings and feedback from users.

The improvements we are looking to do are:

• Add a duckduckgo search box on the top to help them find information in the site. This is a work around for now to the problem of having a way to search the site. It will be the same as Tails that has a search bar using DuckDuckGo: https://tails.boum.org/
• Expand all topics button: #113 (closed)
• Reorganize the sidebar topics aggregating based on themes. Gus will be working on a new list in #99