make custom_keycode_names.md a faq entry instead

reduce space on h3s

break feature_advanced_keycodes.md up into multiple files

improve our docsify setup

fix numbering

overhaul the newbs guide

More sidebar organization

Add API documentation

update flashing.md

- minor typo on intro paragraph (the -> them)
- remove note about :check-size target (`make` task now does this automatically)
- heading level for Caterina commands section
- typo regarding Halfkay (come -> comes)

update newbs_building_firmware.md

Update the text sample for when the compile task completes.

Rework the newbs guide around the qmk cli

Add dark mode support

_summary.md: move Auto Shift page to Software Features category

clean up links to keycode references in newbs_building_firmware_configurator.md

clean up callouts in newbs_building_firmware_configurator.md

remove some unnecessary external links

Also clean up some trailing whitespace.

rework the index page

remove unused docs

more wip

wip