Feat: Tween delaying

.editorconfig

@@ -0,0 +1,3 @@
+[*]
+indent_style = space
+indent_size = 2

docs/index.html

@@ -48,6 +48,7 @@ <h4 class="mt-4 mb-2 Label bg-blue">API</h4>
           <li><code class="text-purple">done</code>: callback function called when tweening is done</li>
           <li><code class="text-purple">easeFunc</code>: function used for easing - default: <code class="text-purple">easeInOutQuart</code></li>
           <li><code class="text-purple">time</code>: time in ms for the tween - default: <code class="text-purple">400</code></li>
+          <li><code class="text-purple">delay</code>: time in ms for the tween to be delay - default: <code class="text-purple">0</code></li>
         </ul>
         <code class="text-purple text-right f5 mr-3">return value</code> <p><code class="text-purple">() =&gt; void</code> - a 'stop' function to stop tweening</p>
       </div>

index.js

@@ -15,17 +15,27 @@ import { easeInOutQuart } from './ease.js'
  * @arg {number} [opts.time = 400] - how long the tween should last
  * @arg {function} [opts.done] - function called when tweening is finished
  * @arg {function} [opts.ease] - function used for easing the tween
+ * @arg {Number} [opts.delay] - Delays the tweened
  * @returns {function} - callback that can stop a tween in progress
  */
-export function tween(from, to, cb, { time = 400, done, ease = easeInOutQuart } = {}) {
+export function tween(from, to, cb, { time = 400, done, ease = easeInOutQuart, delay=0 } = {}) {
   const windowExists = (typeof window !== 'undefined')
   let stopped = false
   const stop = () => stopped = true
   const diff = from - to
   let start = null
+  /**
+   * Step function
+   * @arg {Number} timestamp - the time elsaped since the animation started
+   */
   function step(timestamp) {
     if (stopped) return
-    if (!start) start = timestamp
+    if (!start) start = (timestamp + delay)
+    if (start > timestamp) {
+      window.requestAnimationFrame(step)
+      return
+    }
+
     const progress = timestamp - start
     const percentage = Math.min(progress / time, 1)
     cb(from - ease(percentage) * diff)