Update README.md

Xrysnow · Xrysnow · commit c37c93224e31 · 2022-09-08T17:30:28.000+08:00
diff --git a/README.md b/README.md
@@ -1,3 +1,3 @@
-## cocos2d-x externl
+## cocos2d-x external
 
 This branch adds gfx renderer from [here](https://github.com/Xrysnow/cocos2d-x-gfx).

Original file line number	Diff line number	Diff line change
`@@ -1,3 +1,3 @@`
`1`		`-## cocos2d-x externl`
	`1`	`+## cocos2d-x external`
`2`	`2`
`3`	`3`	`This branch adds gfx renderer from [here](https://github.com/Xrysnow/cocos2d-x-gfx).`