add missing re-exports for layout types #565

Job	Run time
Rustfmt	13s
Clippy	3m 22s
semver	46s
Build Wasm Examples (callback-example)	51s
Build Wasm Examples (basic)	49s
Code Coverage	10s
Build Book	1m 40s
Tests (ubuntu-latest)	2m 2s
Tests (windows-latest)	3m 56s
Build Examples (3d_charts)	24s
Tests (macos-latest)	1m 58s
Build Examples (customization)	31s
Build Examples (images)	39s
Build Examples (maps)	47s
Build Examples (financial_charts)	28s
Build Examples (kaleido)	1m 33s
Build Examples (basic_charts)	25s
Build Examples (scientific_charts)	22s
Build Examples (ndarray)	43s
Build Examples (shapes)	31s
Build Examples (custom_controls)	24s
Build Examples (themes)	33s
Build Examples (subplots)	25s
	23m 32s

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