Add `axum_extra::json!` (#2962) #4889

Job	Run time
cargo-hack	3m 55s
check	1m 36s
cargo-public-api-crates (axum)	33s
check-docs	24s
cargo-public-api-crates (axum-core)	20s
cargo-deny check (advisories)	26s
cargo-public-api-crates (axum-extra)	31s
cargo-deny check (bans licenses sources)	22s
dependencies-are-sorted	21s
cargo-public-api-crates (axum-macros)	22s
Spell Check with Typos	3s
test-versions (stable)	3m 6s
test-versions (beta)	3m 50s
armv5te-unknown-linux-musleabi	29s
test-msrv	2m 17s
test-docs	1m 27s
test-nightly	1m 30s
wasm32-unknown-unknown	27s
	21m 59s

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