feat: add random number generator

Author: jason89521

dev/components/Header.tsx

@@ -1,6 +1,7 @@
 import React from 'react';
 
 import Typist from '../../src';
+import randomDelayGenerator from '../utils/randomDelayGenerator';
 
 export default function Header() {
   return (

dev/utils/randomDelayGenerator.ts

@@ -0,0 +1,3 @@
+export default function randomDelayGenerator(base = 75, bias = 20) {
+  return base + (Math.random() - 0.5) * bias;
+}