[BUG] Handle headers with links

[ccldd]

Issue:

Headers with links are not handled.

Example:

# [Example](http://example.com)

Output:

<!-- TOC -->

- [[Example](http://example.com)](#examplehttpexamplecom)

<!-- /TOC -->

# [Example](http://example.com)

Expected:

<!-- TOC -->

- [Example](#example)

<!-- /TOC -->

# [Example](http://example.com)

[alanwalk]

Hi, i'm sorry for this bug, i will fix it. Thank your~

[bayu01]

You can close this duplicate if you want https://github.com/AlanWalk/markdown-toc/issues/56

[KevinColemanInc]

Still an issue :-/