tree 81b33d2202d1fa59ba21b2cdde241e61664adec8
parent 566e857fff37b8fd760d74042e0b0c04cb43f37d
author Heinrich Schuchardt <xypron.glpk@gmx.de> 1621118068 +0200
committer Heinrich Schuchardt <xypron.glpk@gmx.de> 1621334172 +0200

doc: extension.rst missing in doc/usage/index.rst

'make htmldocs' results in a build warning

    checking consistency... doc/usage/extension.rst:
    WARNING: document isn't included in any toctree

Add the document to the index.

Fixes: 2f84e9cf06d3 ("cmd: add support for a new "extension" command")
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>