update CHANGELOG.md

Author: TinoGuo

CHANGELOG.md

@@ -1,29 +1,28 @@
-## [3.0.0] 2021/07/18
+### [3.0.0] 2021/07/18
 * Support color collection #15
 * Support customize stroke width #15
 * Support customize stroke background #18
 
-## [2.1.1] 2021/05/22
+### [2.1.1] 2021/05/22
 * Bump Dart to 2.13
 
-## [2.0.1] 2021/03/28
+### [2.0.1] 2021/03/28
 * Fix not some animations not working
 
-## [2.0.0] 2021/03/11
+### [2.0.0] 2021/03/11
 * Added support for null safety (Flutter 2.0)
 * Updated deprecated items.
 
-## [1.2.0] - 2020/07/18
+### [1.2.0] - 2020/07/18
 * add `ball_triangle_path_colored`, thanks [Kok Wai Gie](https://github.com/woshikie)
 
-## [1.1.0] - 2019/05/23
+### [1.1.0] - 2019/05/23
 * color is not required, if it is null, it will follow primary color.
 * aspectRatio is 1 to keep all animation play as expected.
 
-## [1.0.0] - 2019/05/14.
+### [1.0.0] - 2019/05/14.
 * improve performance.
 * add chinese readme.
 
-## [0.0.1] - 2019/05/11.
-
+### [0.0.1] - 2019/05/11.
 * initial release.