gckanbun v2.6.0

The gckanbun package provides commands for typesetting Classical Chinese
(Kanbun) with Japanese reading marks, okurigana, ruby, re-reading annotations,
special return marks, and Chinese-poetry layouts.

Version 2.6.0 makes command chaining whitespace-insensitive: a space, line
break, or comment between cooperating commands (for example a ruby or group
ruby followed by okurigana or a return mark) no longer breaks the lookahead or
inserts spurious glue, so spaced and adjacent input now produce identical
layout. Invalid "intrusion" option values are now rejected with a package error
instead of being silently ignored.

This release adds a whitespace regression matrix and a LuaLaTeX-only
"make check" release gate, and drops an unused documentation dependency.

LuaLaTeX remains the recommended engine. Basic (u)pLaTeX compatibility is
retained, with the limitations documented in the package manual.

Repository: https://github.com/munepi/gckanbun
