Add links to buttons on the right

[lucpretti]

These ones:

Please add the following links:

• Register your event - https://docs.google.com/forms/d/e/1FAIpQLScaa4cLVHZJgtYUKUoFPvQBM3u1tZ-SlsDjTlulnWkfD55Hjg/viewform
• Join the community - https://groups.google.com/forum/#!forum/open-data-day