[ICON REQUEST]: MRTK

### I have searched through the issues and didn't find my problem.

- [X] Confirm

### About the icon

Mixed Reality ToolKit is a complex toolkit

### Links and sources

https://en.wikipedia.org/wiki/Mixed_Reality_Toolkit
https://github.com/microsoft/MixedRealityToolkit-Unity
MRTK Logo: https://learn.microsoft.com/en-us/windows/mixed-reality/mrtk-unity/mrtk2/features/images/logo_mrtk_unity_banner.png?view=mrtkunity-2022-05

### Icon links and previews

#### mrtk-original

https://learn.microsoft.com/en-us/windows/mixed-reality/mrtk-unity/mrtk2/features/images/logo_mrtk_unity_banner.png?view=mrtkunity-2022-05

### Additional information

There's a few MRTK icons floating around with a "3", which is the major version 3 of MRTK. I'm not sure it matters. There are no SVG versions available as for as I can tell.