feat(dev): Interactive shell for quick testing/exploration

shell.js

@@ -0,0 +1,39 @@
+/**
+ * ==== wwebjs-shell ====
+ * Used for quickly testing library features
+ * 
+ * Running `npm run shell` will start WhatsApp Web in headless mode 
+ * and then drop you into Node REPL with `client` in its context. 
+ */
+
+const repl = require('repl');
+const fs = require('fs');
+
+const { Client } = require('./index');
+
+const SESSION_FILE_PATH = './session.json';
+let sessionCfg;
+if (fs.existsSync(SESSION_FILE_PATH)) {
+    sessionCfg = require(SESSION_FILE_PATH);
+}
+
+const client = new Client({
+    puppeteer: { headless: false }, 
+    session: sessionCfg 
+});
+
+console.log('Initializing...');
+
+client.initialize();
+
+client.on('qr', () => {
+    console.log('Please scan the QR code on the browser.');
+});
+
+client.on('ready', () => {
+    const shell = repl.start('wwebjs> ');
+    shell.context.client = client;
+    shell.on('exit', async () => {
+        await client.destroy();
+    });
+});