MAJOR - Heading level 1 should be used for the title of the page

[sabderemane]

Major: Certain users are very likely to have difficulty perceiving or operating this.

It visually most prominent heading, ideally not for invisible content ("Django" on homepage). Ideally each page would only have a single h1. (07:04, SC 1.3.1 Info and Relationships).

[specialorange]

https://github.com/django/djangoproject.com/pull/1419