add changelog

Author: d-v-b

changes/3332.feature.md

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+Adds methods to the base `Codec` for creating Zarr V2 or Zarr V3 metadata for a given codec. This removes the distinction between Zarr V2 and Zarr V3 codecs, which will greatly simplify the conversion of Zarr V2 data to Zarr V3.
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+This PR also changes how codecs defined in Numcodecs are handled: When a user attempts to create an array with a numcodecs codec (say, `numcodecs.Blosc`), Zarr will internally replace this codec with the `blosc` codec defined in Zarr. This ensures that Zarr controls the JSON metadata of the codecs we use, and that codecs are uniformly handled internally.
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+Finally, this PR adds support for arbitrary codecs that implement the Numcodecs API. This codecs are wrapped in an adapter layer that imbues them with Zarr V3 codec properties. This adaptation is made on a best-effort basis, and in many cases may not be a substitute for writing a complete Zarr V3 codec.