Playback rate (#411)

* update

packages/artplayer/src/utils/format.js

@@ -2,8 +2,12 @@ export function clamp(num, a, b) {
     return Math.max(Math.min(num, Math.max(a, b)), Math.min(a, b));
 }
 
+export function capitalize(str) {
+    return str.charAt(0).toUpperCase() + str.slice(1);
+}
+
 export function secondToTime(second) {
-    const add0 = num => (num < 10 ? `0${num}` : String(num));
+    const add0 = (num) => (num < 10 ? `0${num}` : String(num));
     const hour = Math.floor(second / 3600);
     const min = Math.floor((second - hour * 3600) / 60);
     const sec = Math.floor(second - hour * 3600 - min * 60);
@@ -13,7 +17,7 @@ export function secondToTime(second) {
 export function escape(str) {
     return str.replace(
         /[&<>'"]/g,
-        tag =>
+        (tag) =>
             ({
                 '&': '&amp;',
                 '<': '&lt;',