clayton craft authored Jun 14, 2021 and Oliver Smith committed Jun 15, 2021

This adds the ability to source any files under
/etc/tinydm.d/$session_type.d, where session_type is either x11 or
wayland. The intention is to allow users to specify variables that
should only be set for specific session types and not others, e.g.
`MOZ_ENABLE_WAYLAND=1` or `SDL_VIDEODRIVER=wayland`.