feat: Add XBM encoder #1612

Job	Run time
build_benchmarks	44s
Fuzz targets (cargo-fuzz)	54s
cargo-deny	17s
Fuzz targets (afl)	2m 26s
cargo-semver-checks	29s
public_private_dependencies	23s
clippy	2m 11s
rustfmt	7s
test_avif_decoding	1m 35s
test_other_archs (powerpc-unknown-linux-gnu)	2m 9s
test_features	20s
test_other_archs (i686-unknown-linux-gnu)	1m 25s
test_toolchains (1.67.1)	46s
test_features (default)	1m 44s
test_toolchains (nightly)	1m 48s
test_features (rayon)	29s
test_toolchains (beta)	1m 23s
test_features (avif)	57s
test_features (bmp)	25s
test_features (dds)	34s
test_features (exr)	33s
test_features (ff)	21s
test_features (gif)	25s
test_features (hdr)	18s
test_features (ico)	32s
test_features (jpeg)	34s
test_features (png)	28s
test_features (pnm)	31s
test_features (qoi)	24s
test_features (tga)	20s
test_features (tiff)	29s
test_features (webp)	22s
test_features (xbm)	17s
	26m 40s

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