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It's small, it's simple, and it's already widely used as part of unixfs.
So there's no reason it shouldn't be part of go-ipld-prime.

The codec is tiny, but has three noteworthy parts: the Encode and Decode
funcs, the cidlink multicodec registration, and the Bytes method
shortcut. Each of these has its own dedicated regression test.

I'm also using this commit to showcase the use of quicktest instead of
go-wish. The result is extremely similar, but with less dot-import
magic. For example, if I remove the Bytes shortcut in Decode:

	--- FAIL: TestDecodeBuffer (0.00s)
	    codec_test.go:115:
	        error:
	          got non-nil error
	        got:
	          e"could not decode raw node: must not call Read"
	        stack:
	          /home/mvdan/src/ipld/codec/raw/codec_test.go:115
	            qt.Assert(t, err, qt.IsNil)