Focus on entryfield "Email or unsername" at login form

Is your feature request related to a problem? Please describe

After loading the LogIn page for administration of Castopod, one must manually focus the first entryfield.

Describe the solution you'd like

The entryfield "Email or unsername" should have the focus on loading the page. No need for manual focusing.

Additional context

It could also be a better accessibility for example for blind users.