update README: bilibili cid

README.md

@@ -104,7 +104,9 @@ var option = {
 
 弹幕
 
-API: `https://api.prprpr.me/dplayer/bilibili?aid=【bilibili视频AV号】`
+API:
+
+`https://api.prprpr.me/dplayer/bilibili?aid=【bilibili视频AV号】` 或 `https://api.prprpr.me/dplayer/bilibili?cid=【bilibili视频cid】`
 
 ```JS
 var option = {
@@ -117,7 +119,9 @@ var option = {
 
 直链
 
-API: `https://api.prprpr.me/dplayer/video/bilibili?aid=【bilibili视频AV号】`
+API:
+
+`https://api.prprpr.me/dplayer/video/bilibili?aid=【bilibili视频AV号】` 或 `https://api.prprpr.me/dplayer/video/bilibili?cid=【bilibili视频cid】`
 
 ```JS
 var xhr = new XMLHttpRequest();