Missing headings on doc pages

[Wryhder]

Some pages are missing a main heading, such as in the screenshot below (Fundamentals > Types of Asterisk Modules). So a user has to check the hamburger menu, address bar, or other means to remember what page they're currently on.

TODO: Update issue with links to all pages with missing main headings

[gtjoseph]

Thanks for the report. I'm going to attempt to correct them in bulk.