Added a section to specify buffer return type (#1691)

Author: melchermaxwell

src/content/chainlink-functions/api-reference/javascript-source.mdx

@@ -59,4 +59,8 @@ The Functions library includes several encoding functions, which are useful for
 | `Functions.encodeInt256`  | Integer          | 32-byte `Buffer` | Converts an integer to a 32-byte `Buffer` for an `int256` in Solidity.         |
 | `Functions.encodeString`  | String           | `Buffer`         | Converts a string to a `Buffer` for a `string` type in Solidity.               |
 
-**Note**: Using these encoding functions is optional. The source code must return a `Buffer` that represents the on-chain bytes array.
+**Note**: Using these encoding functions is optional. The source code must return a [Uint8Array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array) which represents the `bytes` that are returned on-chain.
+
+```javascript
+const myArr = new Uint8Array(ARRAY_LENGTH)
+```