Add API documentation (#4)

Co-authored-by: Kasper Isager Dalsgarð <[email protected]>

README.md

@@ -6,6 +6,54 @@ Cryptographic primitives for JavaScript.
 npm i bare-crypto
 ```
 
+## Usage
+
+```js
+const crypto = require('bare-crypto')
+
+const hash = crypto.createHash('sha256')
+
+hash.update('Hello, world!')
+
+const digest = hash.digest('hex')
+
+console.log(digest)
+```
+
+## API
+
+#### `const hash = createHash(algorithm[, options])`
+
+Create a new `Hash` instance with the specified algorithm and options. The options are passed to [`new Transform()`](https://github.com/mafintosh/streamxts--new-streamtransformoptions).
+
+#### `const bytes = randomBytes(size)`
+
+Generate cryptographically secure random bytes.
+
+#### `randomBytes(size, callback)`
+
+Generate cryptographically secure random bytes, asynchronously providing the result in `callback`. The callback signature is `callback(err, buffer)`.
+
+#### `randomFill(buffer[, offset][, size])`
+
+Fill a buffer with cryptographically secure random bytes.
+
+#### `randomFill(buffer[, offset][, size], callback)`
+
+Fill a buffer with cryptographically secure random bytes, asynchronously providing the result in `callback`. The callback signature is `callback(err, buffer)`
+
+#### `constants.hash`
+
+The supported hash algorithms.
+
+Constant | Description
+--- | ---
+`MD5` | A widely-used 128-bit hash function, now considered insecure due to vulnerabilities to collision attacks. Still fast but not recommended for security-sensitive purposes.
+`SHA1` | A 160-bit hash function, stronger than MD5 but also broken by collision attacks. Deprecated for most cryptographic uses due to security vulnerabilities.
+`SHA256` | Part of the SHA-2 family, this 256-bit hash function is widely used and considered secure for most applications. Slower than MD5 and SHA1 but much more secure.
+`SHA512` | Another member of the SHA-2 family, this 512-bit hash function offers greater security than SHA256 but is slower and produces larger hashes. Suitable for high-security environments.
+`BLAKE2B256` | A fast, secure alternative to SHA-2 designed for efficiency, producing a 256-bit hash. It is optimized for performance while maintaining strong cryptographic security.
+
 ## License
 
 Apache-2.0