Misc WebGL Example Fixes

[aceslowman]

Changes:

• In the Passing Shader Uniforms example I've fixed an issue where the geometry was being displayed mostly off-screen. It should now be centered.
• The Primitives example was missing an ellipsoid shape.
• Multiple Lights example was missing a spotLight().

Additionally I added describe() in each of these example sketches.

For GSOC 2022
mentor: @kjhollen