Make animate_shader example work on WASM

[johanhelsing]

Previously, it would draw nothing and complain with the following
console warnings:

Firefox:

WebGL warning: drawElementsInstanced: Buffer for uniform block is smaller than UNIFORM_BLOCK_DATA_SIZE

Chrome:

[.WebGL-00003B081B72A300] GL_INVALID_OPERATION: It is undefined behaviour to use a uniform buffer that is too small.

Objective

Fixes: #4813

Solution

• I looked at some other code regarding uniforms that worked on wasm and tried to do the same thing (Derive AsStd140 and use std140_size_static).
• Use UniformBuffer and ShaderType
• Add annotation to align to 16 bytes, so WebGL is happy

My understanding of how uniform buffers work is a bit lacking, so please review carefully ;)

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Changelog

• The animate_shader example now works on wasm

[johanhelsing]

Ok, so this needs to be rebased after the encase pr #4339 which changes how uniform buffers are handled.

Seems like ShaderType and its min_size is the thing now, but I can't really test it on wasm yet due to #4811

[johanhelsing]

Rebased after encase migration and the fix for wasm panicking.

Ready for review now :)

[johanhelsing]

No longer relevant, time is exposed through globals (animate_shader example running since 1170b30 #6460)