Update call-to-action button with link to HackUTD VII

[gabriel-flynn]

This latest post on the HackUTD twitter says to go to the link in the bio to register for HackUTD VII but the website is missing the link to the registration page so I changed the following:

• Added a link on the events page to the hackutd vii page (https://2021.gamejam.com)
• One of the buttons on the front page of the website now says "Check out our Hackathon event" instead of "Check out our GameJam event" -> feel free to change the wording on this