Add XBM decoder #1772

Job	Run time
test_toolchains (1.70.0)	40s
test_avif_decoding	1m 36s
test_toolchains (nightly)	1m 8s
test_toolchains (beta)	1m 13s
Fuzz targets (afl)	2m 19s
build_benchmarks	45s
Fuzz targets (cargo-fuzz)	52s
cargo-deny	19s
public_private_dependencies	23s
clippy	2m 13s
rustfmt	12s
test_other_archs (powerpc-unknown-linux-gnu)	2m 48s
test_features	21s
test_other_archs (i686-unknown-linux-gnu)	1m 35s
cargo-semver-checks	30s
test_features (default)	1m 18s
test_features (rayon)	25s
test_features (avif)	1m 3s
test_features (bmp)	36s
test_features (dds)	31s
test_features (exr)	43s
test_features (ff)	30s
test_features (gif)	27s
test_features (hdr)	22s
test_features (ico)	30s
test_features (jpeg)	23s
test_features (png)	27s
test_features (pnm)	22s
test_features (qoi)	26s
test_features (tga)	21s
test_features (tiff)	29s
test_features (webp)	30s
test_features (xbm)	27s
	26m 44s

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