Update maintainer list

[skip ci]

libs/maintainers.txt

@@ -60,6 +60,8 @@ functional/hash       Daniel James <dnljms -at- gmail.com>
 functional/overloaded_function  Lorenzo Caminiti <lorcaminiti -at- gmail.com>
 fusion                Joel de Guzman <joel -at- boost-consulting.com>, Dan Marsden <danmarsden -at- yahoo.co.uk>, Tobias Schwinger <tschwinger -at- isonews2.com>
 geometry              Barend Gehrels <barend -at- xs4all.nl>, Bruno Lalande <bruno.lalande -at- gmail.com>, Mateusz Loskot <mateusz -at- loskot.net>, Adam Wulkiewicz <adam.wulkiewicz -at- gmail.com>
+geometry/extensions   Barend Gehrels <barend -at- xs4all.nl>, Bruno Lalande <bruno.lalande -at- gmail.com>, Mateusz Loskot <mateusz -at- loskot.net>, Adam Wulkiewicz <adam.wulkiewicz -at- gmail.com>
+geometry/index        Barend Gehrels <barend -at- xs4all.nl>, Bruno Lalande <bruno.lalande -at- gmail.com>, Mateusz Loskot <mateusz -at- loskot.net>, Adam Wulkiewicz <adam.wulkiewicz -at- gmail.com>
 gil                   Stefan Seefeld <stefan -at- seefeld.name>, Mateusz Loskot <mateusz -at- loskot.net>
 graph                 K. Noel Belcourt <kbelco -at- sandia.gov>
 graph_parallel        K. Noel Belcourt <kbelco -at- sandia.gov>