Going to help or docs using user menu on mobile changes internal route

Steps to reproduce

What happens?

A new tab opens with the documentation, but in the funkwhale tab a new route is being loaded, which leads to a 404

What is expected?

Only a new tab opens

Context

I guess the issue was introduced here: https://dev.funkwhale.audio/funkwhale/funkwhale/-/blob/develop/front/src/components/Sidebar.vue#L695

Since we are using a <a> tag to go to a normal link, a new route gets pushed even though this does not make sense for external URLs. I am not sure why we introduced it.

Funkwhale version(s) affected: develop