Mesh decals aka floaters or floating geometry is often used to add details to meshes without complicating the underlying geometry and uv mapping.
This PR adds a sample shader that uses a depth offset to ensure floaters are always rendered on top of the underlying geometry. The depth offset is in depth units so there won't be any z-fighting even when viewed from far away.
Furthermore the sample shader utilizes the runtime decal atlas to allow variation between mesh instances with increasing the number of draw calls. The shader works in tandem with the mesh decal component which allows the user to select arbitrary textures that will then be put into the runtime decal atlas. The component feeds the runtime decal indices as custom data per instance to the shader.
The shader uses the integer part of the UV coordinates to identify which decal slot should be used. There can be up to 8 slots per mesh:

The sample shader only supports base color from the runtime decal atlas and an additional alpha texture per material. The shader and also the component is meant as a starting point and can be customized to the individual needs of the user.