Add demo of how to read plot state _before_ showing the plot #8810

Job	Run time
android	20s
Format + check + test	5m 19s
Check wasm32 + wasm-bindgen	2m 47s
cargo-deny aarch64-apple-darwin	39s
Check Windows	1m 25s
cargo-deny aarch64-linux-android	42s
cargo-deny i686-pc-windows-gnu	39s
cargo-deny i686-pc-windows-msvc	40s
cargo-deny i686-unknown-linux-gnu	42s
cargo-deny wasm32-unknown-unknown	42s
cargo-deny x86_64-apple-darwin	38s
cargo-deny x86_64-pc-windows-gnu	43s
cargo-deny x86_64-pc-windows-msvc	40s
cargo-deny x86_64-unknown-linux-gnu	38s
cargo-deny x86_64-unknown-linux-musl	39s
cargo-deny x86_64-unknown-redox	39s
	17m 52s

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