Fix the logo in header not being an anchor link.

## What does this MR do?

Adds an actual link to the Tanuki in the header instead of a `Turbolinks.visit()`.

## Are there points in the code the reviewer needs to double check?

Do we care that this reverts the Safari issue fixed in !2690? I feel bad, but it's hacky and there's not a great way to fix it here.

## Why was this MR needed?

You couldn't open the home page in a new tab before, it was very annoying.

## What are the relevant issue numbers?

Fixes #18604 

cc: @rspeicher 

See merge request !4661