(so that we can avoid a broken link in a wiki page we're migrating)

ref:
https://docs.civicrm.org/dev/en/latest/documentation/style-guide/#parts-chapters-sections

https://wiki.civicrm.org/confluence/display/CRMDOC/Add-on+Formats

https://wiki.civicrm.org/confluence/display/CRMDOC/Cache+Reference

Auto-import with no edits

from:
https://wiki.civicrm.org/confluence/display/CRMDOC/API+Architecture+Standards

Direct import (no modifications).

Reorder requirements docs into the basics section and move devloping civicrm into core and add backdrop in

Reorder extensions files and rename to be extension structure to be clear its more than just files its directory strcutre and improve doc a bit

Move them into the dedicated page on PhpStorm. Why? Tim has expressed
some concern about the potential difficulty (and slippery slope) of
starting to maintain IDE-specific docs. I like the PhpStorm page, but I
can see where he's coming from to a certain extent. As such, I think it
will be a good compromise if we can keep all the IDE-specific stuff as
consolidated as possible.

ref:
https://docs.civicrm.org/dev/en/latest/documentation/style-guide/#parts-chapters-sections