FAL-242 add logos and initial theme overrides

FAL-242

This adds the initial client logos and theme overrides to match their designs.

Screenshots:

Test instructions:

• set up the frontend (see opencraft/dev/frontend-app-course-search!7 (merged) )
• clone this repository and install it in the frontend environment, under the @edx/brand alias: npm install --no-save @edx/brand@file:path/to/this/repository
• start the frontend and view it in the browser
• verify that it matches the client designs (see FAL-242). This doesn't need to be perfect; we have another iteration on this planned soon, with feedback recently obtained from the client.
• check the readme for accuracy

Reviewers:

• @tartansandal