[docs] Fix syntac error

[iamchenxin]

Split {{ in example code to avoid an Exception in jekyll.

Liquid Exception: Variable '{{' was not properly terminated with regexp: /}}/ in docs/10.1-animation.md

[zpao]

Thanks. The Liquid preprocessing can be annoying and I always forget about this. In the past we've just done {{"{{"}} to make Liquid print the literal double brace.

[chargeOne]

?

[zpao]

@zhuyan730 there are issues rendering {{ in Jekyll due to its parser which runs before markdown processing. This avoids it.