Re: [PATCH 4/5] doc: use .adoc extension for AsciiDoc files

>
> We presently use the ".txt" extension for our AsciiDoc files.  While not
> wrong, most editors do not associate this extension with AsciiDoc,
> meaning that contributors don't get automatic editor functionality that
> could be useful, such as syntax highlighting and prose linting.
>
> It is much more common to use the ".adoc" extension for AsciiDoc files,
> since this helps editors automatically detect files and also allows
> various forges to provide rich (HTML-like) rendering.  Let's do that
> here, renaming all of the files and updating the includes where
> relevant.  Adjust the various build scripts and makefiles to use the new
> extension as well.