docs: missing import in ClientCredentials example (#427)

Author: ewanharris

config/clients/js/template/README_initializing.mustache

@@ -17,7 +17,7 @@ const fgaClient = new {{appShortName}}Client({
 #### API Token
 
 ```javascript
-const { {{appShortName}}Client } = require('{{packageName}}'); // OR import { {{appShortName}}Client } from '{{packageName}}';
+const { {{appShortName}}Client, CredentialsMethod } = require('{{packageName}}'); // OR import { {{appShortName}}Client, CredentialsMethod } from '{{packageName}}';
 
 const fgaClient = new {{appShortName}}Client({
   apiUrl: process.env.FGA_API_URL, // required
@@ -35,7 +35,7 @@ const fgaClient = new {{appShortName}}Client({
 #### Client Credentials
 
 ```javascript
-const { {{appShortName}}Client } = require('{{packageName}}'); // OR import { {{appShortName}}Client } from '{{packageName}}';
+const { {{appShortName}}Client, CredentialsMethod } = require('{{packageName}}'); // OR import { {{appShortName}}Client, CredentialsMethod } from '{{packageName}}';
 
 const fgaClient = new {{appShortName}}Client({
   apiUrl: process.env.FGA_API_URL, // required