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>

diff --git a/doc/usage/index.rst b/doc/usage/index.rst
index 6f45fd3..c1f9b6a 100644 (file)
--- a/doc/usage/index.rst
+++ b/doc/usage/index.rst
@@ -26,6 +26,7 @@ Shell commands
    conitrace
    echo
    exception
+   extension
    exit
    false
    fatinfo