Precision limit

[Silzinc]

After trying to zoom on the fractal, after a certain level, it becomes impossible to drag the scene, and the fractal is just made of fat squares and rectangles. This is clearly caused by the limited precision of the f32 type. I found 2 solutions so far to enable a deeper zoom, although this problem will always comeback at a certain point:

1. We can replace WGSL by GLSL which supports double precision floats. However, this won't be possible for now as bevy's GLSL does not support #import instructions yet. See https://github.com/bevyengine/bevy/blob/main/assets/shaders/custom_material.frag.
2. Scale everything up. Currently, the screen shows a small part of the complex plane, and the distances we work with are never above 1 in order of magnitude. This is a waste of exponent bits.

[Silzinc]

Update on this one : scaling up does not change the result. The problem is that the difference in color between adjacent pixels becomes negligible compared to the value of the complex numbers in said pixels. Only double precision can fix that.