v2-docs: Add pre transform and chart state docs #1026

Job	Run time
build-vegafusion-wasm	8m 27s
test-rust (ubuntu-20.04)	24m 1s
build-vegafusion-python-linux-arm64	3m 24s
build-vegafusion-python-linux-64	3m 3s
build-vegafusion-python-osx-64	18m 31s
test-rust (windows-2022)	40m 1s
test-rust (macos-14)	22m 3s
build-vegafusion-python-win-64	32m 1s
build-vegafusion-python-osx-arm64	12m 2s
build-vegafusion-server-linux-arm64	2m 0s
build-vegafusion-server-linux-64	9m 0s
build-vegafusion-server-osx-64	33m 23s
build-vegafusion-server-osx-arm64	11m 27s
build-vegafusion-server-win-64	31m 28s
check-rust	3m 44s
check-vegafusion-python	2m 28s
test-vegafusion-python-linux-64	26m 6s
test-vegafusion-python-osx-arm64	49s
test-vegafusion-python-win-64	1m 38s
	4h 45m 36s

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