Significant remaining TBD:

Math markup
Greek letter attributes - define & expand in [source]
Tables
Links (https references)
Internal xrefs/anchors
Citations/references
Appendix titles / formats
Odd bit-packing diagrams
Figure out how to dynamically? incorporate REFERENCE.adoc (would be by
    far easiest to statically generate it from wetzel repository and
    commit here - can't imagine it will often change).

Add anchors to sections, matching titles (might also match Asciidoc default behavior if no explicit anchor).
Remove some extraneous  

github, rather than the local repository branch (since there may not be
a local branch, depending on how the spec is built and viewed - and the
master branch registry should be canonical, as well).

markup problems.

Makefile for building and intermediate generated files, and tweakups
markup of the math-rendering URLs to work properly with asciidoctor.

https://github.com/KhronosGroup/glTF/pull/1901/files#r523465257

… numbers

Use npx to invoke wetzel now that it's in npm (@donmccurdy)

host the generated specification on github and are not constrained by
the limitations of its asciidoctor implementation.

Also cleans up the Makefile a bit to explain the wetzel invocation and
the URL argument to it ($(SCHEMALINK)).

Try to use Github Actions for CI test that builds the spec targets.

With help from CesiumGS/wetzel#51

Add JSON schemas to AsciiDoctor output.

See discussion:
#1907 (comment)

latexmath rendering vs. the image approaches previously used. See the
generated HTML / PDF in the Actions artifacts download and search for
"Latexmath" (followed by "Old") versions of each equation.

Relevant points:

* The HTML output is not self-contained. It introduces an external dependency on the MathJax package on a CDN outside our control.
* MathJax runs after the HTML page is loaded and takes noticeable time - initially you will see the raw latex markup, replaced and re-laid-out with the formatted math.
* The PDF output introduces a new dependency on the asciidoctor-mathematical gem (the Khronos Docker image already has this).
* The PDF math rendering quality is noticeably lower than the HTML rendering quality.

Compare latexmath to image math rendering in asciidoctor branch

document; revised to what appears to be a stable location at Disney. The
Pharr citation was mis-dated; the 3rd edition of the book was published
in 2016, not 2018 (although the website lists 2018 as the latest
copyright date).

In principle these changes belong in the currently canonical Markdown
spec as well, but they're trivial changes and probably can just be
deferred to when the WG switches over to the asciidoctor markup.

Sectioned hanging text

See #1901 (comment)

Note: doing this for HTML is harder.

Flip credits & copyrights

Co-authored-by: Ed Mackey <elm19087@gmail.com>

#2022

* Integrate latest updates

* More typography fixes

* Apply suggestions from code review

Co-authored-by: Gary Hsu <bghgary@users.noreply.github.com>

* Address feedback

* Address feedback & add more clarifications

* Address feedback

Co-authored-by: Gary Hsu <bghgary@users.noreply.github.com>

* Add license text of all licenses used under LICENSES/.
* Add copyright statements that are readable by REUSE where reasonably possible.
* Add .reuse/dep5 entry as fallback licenses for images etc. where explicit copyrights not possible.
* Add 'reuse lint' check to github Actions CI
* Use 'TBD' license on vendor extensions, none of which seem to have explicit licenses and may not be owned by Khronos.
* Some minor whitespace / EOL convention changes.
* Add boilerplate files missing from repo such as CONTRIBUTING and COPYING.