Make "Back to Main Page" button on instructions page more robust

[kiphenglim]

Currently, the button for redirecting users back to the main page of the website is a simple back button that uses the user's history. This doesn't work if the user has navigated directly to the instructions page, for example. Additionally, if the user has previously uploaded an image, navigates to the instructions page, and then attempts to go back, the browser may ask if they want to resubmit the form.

Ideally, we would navigate directly to the homepage link and give them a fresh version of the site.