Improve doc for BodyWithConfig #2693

Job	Run time
build_versions (stable)	23s
cargo-deny (aarch64-apple-ios)	19s
build_versions (beta)	16s
Test	58s
cargo-deny (aarch64-linux-android)	21s
build_versions (1.71.1)	16s
Test	1m 5s
Test (charset)	1m 4s
cargo-deny (i686-pc-windows-gnu)	20s
Test (cookies)	1m 3s
Test (charset)	1m 8s
cargo-deny (i686-pc-windows-msvc)	21s
Docs	1m 47s
Test (socks-proxy)	54s
Test (cookies)	1m 12s
cargo-deny (i686-unknown-linux-gnu)	21s
Test (gzip)	54s
Test (socks-proxy)	1m 8s
cargo-deny (wasm32-unknown-unknown)	19s
Test (brotli)	1m 0s
Test (gzip)	1m 7s
Test (json)	59s
Lint	41s
cargo-deny (x86_64-apple-darwin)	19s
Test (brotli)	1m 5s
Test (native-tls)	1m 4s
Test (json)	1m 3s
cargo-deny (x86_64-apple-ios)	19s
Test (rustls-no-provider)	1m 8s
cargo-deny (x86_64-pc-windows-gnu)	18s
Test (native-tls)	1m 10s
cargo-deny (x86_64-pc-windows-msvc)	21s
cargo-deny (x86_64-unknown-linux-gnu)	20s
cargo-deny (x86_64-unknown-redox)	20s
	25m 23s

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