Improve doc for BodyWithConfig #2695

Job	Run time
build_versions (stable)	22s
Test	1m 10s
build_versions (beta)	3m 20s
Test	54s
Test (charset)	1m 0s
build_versions (1.71.1)	22s
Test (charset)	1m 2s
Test (cookies)	1m 15s
cargo-deny (aarch64-apple-ios)	21s
Test (cookies)	53s
Test (socks-proxy)	1m 3s
cargo-deny (aarch64-linux-android)	22s
Docs	1m 56s
Test (socks-proxy)	49s
Test (gzip)	1m 4s
cargo-deny (i686-pc-windows-gnu)	20s
Test (brotli)	1m 1s
Test (gzip)	1m 21s
cargo-deny (i686-pc-windows-msvc)	22s
Test (json)	1m 16s
Test (brotli)	1m 1s
Lint	43s
cargo-deny (i686-unknown-linux-gnu)	19s
Test (native-tls)	1m 9s
Test (json)	52s
Test (native-tls)	54s
cargo-deny (wasm32-unknown-unknown)	24s
Test (rustls-no-provider)	1m 9s
cargo-deny (x86_64-apple-darwin)	20s
cargo-deny (x86_64-apple-ios)	19s
cargo-deny (x86_64-pc-windows-gnu)	20s
cargo-deny (x86_64-pc-windows-msvc)	19s
cargo-deny (x86_64-unknown-linux-gnu)	21s
cargo-deny (x86_64-unknown-redox)	18s
	28m 41s

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