Updates API doc

Author: hazmatzo

API.md

@@ -11,7 +11,7 @@
 * [client.cat](#clientcat)
 * [client.import](#clientimport)
 * [client.listAsks](#clientlistasks)
-* client.payments
+* [client.payments](#clientpayments)
 * client.proposeStorageDeal
 * client.queryStorageDeal
 * [config.get](#configget)
@@ -401,6 +401,46 @@ After first iteration:
 */
 ```
 
+## `client.payments`
+
+> List payments for a given deal
+
+### `client.payments([options])`
+
+#### Parameters
+
+| Name | Type | Description |
+|------|------|-------------|
+| channel id | `String` | Channel id from which to list vouchers |
+| options | `Object` | Optional options |
+| options.signal | [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal) | A signal that can be used to abort the request |
+
+#### Returns
+
+| Type | Description |
+|------|-------------|
+| `Promise<Object[]>` | List of payments |
+
+```js
+const cid = 'zDPWYqFCuTNxiwRkt1iDJWEy6qKPGCunMGHrP1ojsMrZDWKYsgzF'
+const payments = await fc.client.payments(cid)
+console.log(payments)
+
+/*
+  [
+    {
+      "channel":0,
+      "payer":"t1bcvxo4ztdkukjmrsjvc5d4w24cl55vvbrssspyy",
+      "target":"t1uo4nzu44apoclkbjbbvc4f3irbptg3ctjq44wiq",
+      "amount":"25000",
+      "valid_at":8,
+      "condition":null,
+      "signature":"1My76149fPIulbdO/DKlkUBMMSLwGYSw2XmVKXq3HrxMG5kkmBgsaPZ/DzdxiOWX5kdnXJ++AFQqsmWHd5dtOwE="
+    }
+  ]
+*/
+```
+
 ## `config.get`
 
 > Get config values