Update the Handling of 404 Errors

[ryangchung]

When trying to go to a page which does not exist, the current behavior is that it lands on this text:

It then it redirects to https://carletoncomputersciencesociety.github.io/<anything> (the legacy website), which is not hosted anymore.

1. Redirect to the home page, https://ccss.carleton.ca instead of the legacy link.
2. Change the content from a to b.

a.

We are currently in the process of migrating to our new website!
You are likely looking for a page from our legacy site and will momentarily be redirected.
Sorry for the inconvenience.

b.

You have reached a page which does not exist. It may have been deleted, or has never existed.
You will be momentarily redirected back to the home page.
Sorry for the inconvenience.