wechatMarkdown cannot handle cascaded brackets

[zhongdongy]

The converter takes first open bracket and close with first ] that may not match with the actual URL component.

Input

This is an example [of cascaded brackets with [link inside](https://github.com) it].

Expected output

This is an example [of cascaded brackets with <url-text>link inside</url-text> it].

- <url-text-note>link inside</url-text-note><url>https://github.com</url>

Actual output

This is an example <url-text>of cascaded brackets with [link inside</url-text> it].

- <url-text-note>of cascaded brackets with [link inside</url-text-note><url>https://github.com</url>