Add a DeviceRGB create menu that creates a new material with correct settings

[pramberg]

Description

I realized that it is error prone to make the user deal with all the material settings when creating a new material. It would be easier if that is done automatically. I don't think it should be too difficult to add, IIRC

Requirements

• [x] New item in the Add new asset menu called "DeviceRGB Material" or something like that
• [x] The created material should have the Material Domain set to Post Process
• [x] The created material should have Output Alpha set to True
• [x] Update the Getting Started guide with the simplified steps

[pramberg]

This was added in 601227dc4235e36d4d9133d03f0864835544d35e. Getting Started has been updated!