[Wish] Register all addon keywords in main Keywords Index of all GRASS GIS modules

[neteler]

Describe the wish

So far the keywords of GRASS GIS addons are not yet added to (injected):

Keywords - Index of GRASS GIS modules https://grass.osgeo.org/grass-stable/manuals/keywords.html

This being solved during addon compilation would greatly increase the visibility of the GRASS GIS addons.