update authors list to include 2.1.0 and dev branch contributors
update authors list to include 2.1.0 and dev branch contributors

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