Updated docs theme truncates the API Guide navigation list of subsections

[patdahl]

I don't know mkdocs particularly well, so I haven't had the time to investigate thoroughly, but I just noticed that the side navigation in the API Guide in the docs only shows links for the subheadings under the first main heading for a given category. So, for example, the "Serializers" topic only shows links for subheadings under #Serializers in the docs file, and that's it. None of the sections for #ModelSerializer are listed and if you scroll into that section the navigation just shows Including extra content from the #Serializers section as the implied active subheading. Permanent links for the unlisted sections seem to work fine so I assume that it is just an issue with how the navigation is rendered.

[browniebroke]

Good catch, I wonder if it's because both Serializers and ModelSerializer are <h1> tags in the HTML. A HTML page is supposed to have only one <h1> tag. There is also an option to put the current page heading on the right side instead of nested under the sections

[browniebroke]

Fixed in #9909