Add ES256K sign and verify test vectors

Signed-off-by: Frank Hinek <[email protected]>

web5-test-vectors/crypto_es256k/README.md

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+# `ES256K` Test Vectors
+
+This directory contains test vectors for the secp256k1 with SHA-256 signature scheme, which is a
+part of the Elliptic Curve Digital Signature Algorithm (ECDSA) family of signature algorithms as
+detailed in the Standards for Efficient Cryptography Group (SECG) publication
+[SEC1](https://www.secg.org/sec1-v2.pdf).
+
+The `ES256K` algorithm identifier is defined in
+[RFC8812](https://datatracker.ietf.org/doc/html/rfc8812), which specifies the use of ECDSA with the
+secp256k1 curve and the SHA-256 cryptographic hash function.
+
+> [!IMPORTANT]
+> All ECDSA signatures, regardless of the curve, are subject to signature malleability such that
+> for every valid signature there is a "mirror" signature that's equally valid for the same message
+> and public key. Read more
+> [here](https://github.com/TBD54566975/web5-js/blob/f4e8194301be302889c031fb904425ff1a7b34aa/packages/crypto/src/primitives/secp256k1.ts#L75-L101)
+> about the practical implications and mitigation techniques.
+
+## `sign`
+
+Sign test vectors are detailed in a [JSON file](./sign.json). It includes cases for testing the
+signing operation with the secp256k1 curve and SHA-256 hash function.
+
+### Input
+
+The `input` for the sign operation is an object with the following properties:
+
+| Property | Description                                                          |
+| -------- | -------------------------------------------------------------------- |
+| `key`    | A JSON Web Key ([JWK][RFC7517]) object representing the private key. |
+| `data`   | The data to be signed, as a byte array in hexadecimal string format. |
+
+### Output
+
+The `output` is a hexadecimal string representing the signature byte array produced by the signing
+operation.
+
+### Reference Implementations
+
+Reference implementations for the sign operation can be found in the following SDK repositories:
+
+- TypeScript: [`Secp256k1.sign()`](https://github.com/TBD54566975/web5-js/blob/44c38a116dec0b357ca15d807eb513f819341e50/packages/crypto/src/primitives/secp256k1.ts#L547-L595)
+
+## `verify`
+
+Verify test vectors are outlined in a [JSON file](./verify.json), encompassing both successful and unsuccessful signature verification cases.
+
+### Input
+
+The `input` for the verify operation includes:
+
+| Property    | Description                                                                      |
+| ----------- | -------------------------------------------------------------------------------- |
+| `key`       | An JSON Web Key ([JWK][RFC7517]) object representing the public key.             |
+| `signature` | The signature to verify, as a byte array in hexadecimal string format.           |
+| `data`      | The original data that was signed, as a byte array in hexadecimal string format. |
+
+### Output
+
+The `output` is a boolean value indicating whether the signature verification was successful
+(`true`) or not (`false`).
+
+### Reference Implementations
+
+Reference implementations for the verify operation can also be found in the following SDK
+repositories:
+
+- TypeScript: [`Secp256k1.verify()`](https://github.com/TBD54566975/web5-js/blob/44c38a116dec0b357ca15d807eb513f819341e50/packages/crypto/src/primitives/secp256k1.ts#L670-L724)
+
+[RFC7517]: https://datatracker.ietf.org/doc/html/rfc7517