Sarah White authored Dec 04, 2020 and Dan Allen committed Feb 16, 2021

* migrate AsciiDoc syntax quick reference
* revise commentary and improve examples
* use ~ to denote autowidth column
* add collapsible attribute to enable the extension to backport the collapsible block
* rewrite intro
* change URI to URL
* add note that empty block attribute list can be used to separate lists
* clarify that unordered list marker can be changed using style
* remove note about font-based and interactive checklists
* remove note about sectlinks and sectanchors
* include the term "literal monospace"
* add example of possessive monospace
* rename and reorder sections
* add custom inline role example

Co-authored-by: Dan Allen <dan.j.allen@gmail.com>