docs: add usage example

src/errors.ts

@@ -4,19 +4,5 @@ export enum codes {
   ERR_INVALID_PARAMETERS = 'ERR_INVALID_PARAMETERS',
   ERR_INVALID_CMS = 'ERR_INVALID_CMS',
   ERR_MISSING_KEYS = 'ERR_MISSING_KEYS',
-  ERR_NO_KEY = 'ERR_NO_KEY',
-  ERR_INVALID_KEY_NAME = 'ERR_INVALID_KEY_NAME',
-  ERR_INVALID_KEY_TYPE = 'ERR_INVALID_KEY_TYPE',
-  ERR_KEY_ALREADY_EXISTS = 'ERR_KEY_ALREADY_EXISTS',
-  ERR_INVALID_KEY_SIZE = 'ERR_INVALID_KEY_SIZE',
-  ERR_KEY_NOT_FOUND = 'ERR_KEY_NOT_FOUND',
-  ERR_OLD_KEY_NAME_INVALID = 'ERR_OLD_KEY_NAME_INVALID',
-  ERR_NEW_KEY_NAME_INVALID = 'ERR_NEW_KEY_NAME_INVALID',
-  ERR_PASSWORD_REQUIRED = 'ERR_PASSWORD_REQUIRED',
-  ERR_PEM_REQUIRED = 'ERR_PEM_REQUIRED',
-  ERR_CANNOT_READ_KEY = 'ERR_CANNOT_READ_KEY',
-  ERR_MISSING_PRIVATE_KEY = 'ERR_MISSING_PRIVATE_KEY',
-  ERR_INVALID_OLD_PASS_TYPE = 'ERR_INVALID_OLD_PASS_TYPE',
-  ERR_INVALID_NEW_PASS_TYPE = 'ERR_INVALID_NEW_PASS_TYPE',
-  ERR_INVALID_PASS_LENGTH = 'ERR_INVALID_PASS_LENGTH'
+  ERR_NO_KEY = 'ERR_NO_KEY'
 }

src/index.ts

@@ -1,3 +1,28 @@
+/**
+ * @packageDocumentation
+ *
+ * Cryptographically protected messages using the libp2p keychain
+ *
+ * @example
+ *
+ * ```typescript
+ * import { createLibp2p } from 'libp2p'
+ * import { CMS } from '@libp2p/cms'
+ *
+ * // Create a libp2p node
+ * const node = await createLibp2p({
+ *   // ...other options
+ *   connectionEncryption: [plaintext()]
+ * })
+ *
+ * const cms = new CMS(libp2p.keychain)
+ *
+ * // Use CMS operations
+ * const plaintext = Uint8Array.from([0, 1, 2, 3])
+ * const ciphertext = await cms.encrypt('key-name', plaintext)
+ * ```
+ */
+
 import 'node-forge/lib/pkcs7.js'
 import 'node-forge/lib/pbe.js'
 // @ts-expect-error types are missing