fix: readme usage example (#253)

* Fix readme usage example

- Fixes #252

* fix: lint

Co-authored-by: Marin Petrunic <marin.petrunic@gmail.com>

Author: TimDaub

README.md

@@ -25,14 +25,15 @@ Install with `yarn add @chainsafe/libp2p-noise` or `npm i @chainsafe/libp2p-nois
 Example of using default noise configuration and passing it to the libp2p config:
 
 ```js
-import {Noise} from "@chainsafe/libp2p-noise"
+import {noise} from "@chainsafe/libp2p-noise"
 
 //custom noise configuration, pass it instead of `new Noise()`
-const noise = new Noise(privateKey, Buffer.alloc(x));
+//x25519 private key
+const n = noise(privateKey);
 
 const libp2p = new Libp2p({
    modules: {
-     connEncryption: [new Noise()],
+     connEncryption: [noise()],
    },
 });
 ```

test/index.spec.ts

@@ -3,6 +3,7 @@ import { expect } from 'aegir/chai'
 import { duplexPair } from 'it-pair/duplex'
 import { pbStream } from 'it-pb-stream'
 import sinon from 'sinon'
+import { noise } from '../src/index.js'
 import { Noise } from '../src/noise.js'
 import { createPeerIdsFromFixtures } from './fixtures/peer.js'
 
@@ -15,10 +16,10 @@ function createCounterSpy () {
 
 describe('Index', () => {
   it('should expose class with tag and required functions', () => {
-    const noise = new Noise()
-    expect(noise.protocol).to.equal('/noise')
-    expect(typeof (noise.secureInbound)).to.equal('function')
-    expect(typeof (noise.secureOutbound)).to.equal('function')
+    const noiseInstance = noise()()
+    expect(noiseInstance.protocol).to.equal('/noise')
+    expect(typeof (noiseInstance.secureInbound)).to.equal('function')
+    expect(typeof (noiseInstance.secureOutbound)).to.equal('function')
   })
 
   it('should collect metrics', async () => {