added missing file extension filter to doc build file
added missing file extension filter to doc build file

killerantz/HoloToolkit-Unity,vladkol/MixedRealityToolkit-Unity,DDReaper/MixedRealityToolkit-Unity,killerantz/HoloToolkit-Unity,vladkol/MixedRealityToolkit-Unity,vladkol/MixedRealityToolkit-Unity,killerantz/HoloToolkit-Unity,killerantz/HoloToolkit-Unity