docs: update correct Big-O chart (#62)

README.md

@@ -191,7 +191,7 @@ npm test -- -t 'playground'
 
 Order of growth of algorithms specified in Big O notation.
 
-![Big O graphs](https://github.com/trekhleb/javascript-algorithms/blob/master/assets/big-o-graph.png?raw=true)
+![Big O graphs](./assets/big-o-graph.png)
 
 Source: [Big O Cheat Sheet](http://bigocheatsheet.com/).
 

README.zh-CN.md

@@ -170,7 +170,7 @@ npm test -- -t 'playground'
 
 大O符号中指定的算法的增长顺序。
 
-![Big O graphs](https://github.com/trekhleb/javascript-algorithms/blob/master/assets/big-o-graph.png?raw=true)
+![Big O graphs](./assets/big-o-graph.png)
 
 源: [Big O Cheat Sheet](http://bigocheatsheet.com/).
 

README.zh-TW.md

@@ -167,7 +167,7 @@ npm test -- -t 'playground'
 
 特別用大 O 標記演算法增長度的排序。
 
-![Big O 表](https://github.com/trekhleb/javascript-algorithms/blob/master/assets/big-o-graph.png?raw=true)
+![Big O 表](./assets/big-o-graph.png)
 
 資料來源: [Big O Cheat Sheet](http://bigocheatsheet.com/).