chore: add example for a simple regex match on an input (#1087)

Co-authored-by: Simon Boudrias <admin@simonboudrias.com>

Author: lukeocodes

packages/inquirer/examples/regex-validate-input.js

@@ -0,0 +1,25 @@
+/**
+ * Filter and validate progress example
+ */
+
+'use strict';
+const inquirer = require('..');
+
+const questions = [
+  {
+    type: 'input',
+    name: 'api_key',
+    message: 'Please enter a valid API key.',
+    validate(input) {
+      if (/([a-f0-9]{40})/g.test(input)) {
+        return true;
+      }
+
+      throw Error('Please provide a valid API key secret.');
+    },
+  },
+];
+
+inquirer.prompt(questions).then((answers) => {
+  console.log(JSON.stringify(answers, null, '  '));
+});