Add Glow Material / Layer to Post Processing

[lalalune]

Is your feature request related to a problem? Please describe.
In Babylon.js by default (and many other engines as an add-on) you can add glow to objects. This is ideal for objects such as lightsabers.

Describe the solution you'd like
We should add a post processing option for glow to our post processing application. If it is enabled, we will turn on the glow layer for objects that have a glow material. We will also need to implement a WebaverseGlowMaterial or something like that on the other side.

I'm really looking for sci fi glow for things like space ships engines, lightsabers, headlights, etc where bloom is okay but not quite enough to capture the vibe.