Docs should be divided up into sections instead of one long usage page

[kethinov]

this is referring to the docs app within this repo's "usage" page to divide up the usage page into smaller, more purposeful / topical pages

but the fullDemo page could be potentially divided up better too. not into separate pages, but make better / more consistent use of fieldsets/legends to make the page look cleaner. ideally divide it up into the same categories as the changes made to the above