Add optional serde feature for image::ImageFormat (#2374) #1681

Job	Run time
cargo-deny	17s
Fuzz targets (afl)	2m 11s
build_benchmarks	48s
Fuzz targets (cargo-fuzz)	50s
cargo-semver-checks	35s
clippy	2m 4s
public_private_dependencies	23s
rustfmt	14s
test_avif_decoding	1m 25s
test_features	38s
test_toolchains (1.70.0)	47s
test_features (default)	1m 52s
test_other_archs (powerpc-unknown-linux-gnu)	3m 8s
test_toolchains (nightly)	1m 52s
test_features (rayon)	33s
test_other_archs (i686-unknown-linux-gnu)	2m 2s
test_toolchains (beta)	2m 2s
test_features (avif)	1m 2s
test_features (bmp)	35s
test_features (dds)	39s
test_features (exr)	54s
test_features (ff)	34s
test_features (gif)	34s
test_features (hdr)	34s
test_features (ico)	42s
test_features (jpeg)	33s
test_features (pcx)	28s
test_features (png)	36s
test_features (pnm)	5m 10s
test_features (qoi)	30s
test_features (tga)	28s
test_features (tiff)	38s
test_features (webp)	32s
	36m 10s

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