Render/Light layers data in shader example

## What problem does this solve or what need does it fill?
Add example of Render/Light layers data used in shader.

## What solution would you like?
Similarly to volumetric light:
`
#import bevy_pbr::mesh_view_types::DIRECTIONAL_LIGHT_FLAGS_VOLUMETRIC_BIT
....
if (((*light).flags & DIRECTIONAL_LIGHT_FLAGS_VOLUMETRIC_BIT) == 0)
{
......
}
.....
`
If specific post-fx (or shader in general) is requesting light data, only lights with particular u32 is used.

Close, but not exact example form existing games/media is
something that remotely resembles magic lamp from 2015 game _The Witcher 3_ by CDPR.

Disclaimer:
1 I HAVE NO IDEA HOW IT IS IMPLEMENTED IN MENTIONED GAME
2 I HAVE NO RELATION TO CDPR
3 THIS MENTION OF GAME ISN'T SPONSORED OR PAID

Main idea is to have simple and reusable system.
It should work with all types of lights, not only directional.

## Proposed workflow
1. Set struct _light.shader_layer_ bits u32 in rust code
2. Use it in wgsl code _(*light).shader_layer_