Split layout into multiple modules #524

Job	Run time
Rustfmt	15s
Clippy	23s
Tests (ubuntu-latest)	21s
Tests (windows-latest)	8s
semver	9s
Build Wasm Examples (basic)	23s
Tests (macos-latest)	23s
Build Wasm Examples (callback-example)	22s
Build Examples (basic_charts)	22s
Code Coverage	10s
Build Examples (kaleido)	23s
Build Examples (3d_charts)	22s
Build Examples (financial_charts)	21s
Build Examples (shapes)	22s
Build Examples (maps)	23s
Build Examples (ndarray)	22s
Build Examples (images)	21s
Build Examples (custom_controls)	21s
Build Examples (scientific_charts)	21s
Build Examples (subplots)	23s
	6m 35s

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