Issues with link format / regex

[MarketingPip]

There is an issue with the link formatting. Example's provided below to re-produce this issue.

This link will NOT be parsed properly by.

[here](https://github.com/showdownjs/showdown/wiki/Showdown's-Markdown-syntax)

This will parse properly.

[here](https://github.com/showdownjs/showdown/wiki/Showdown)

This will NOT be.

[here](https://github.com/showdownjs/showdown/wiki/Showdown's)

Note: I recall in previous versions this did not seem occur & don't know if the function was changed etc since then.

ps; hoping to add a small contribution soon (not relating to this). Keep posted.

[MarketingPip]

Version /*! showdown v 2.1.0 - 21-04-2022 */

does NOT have this issue

tho the version used in the demo

/*! showdown v 3.0.0-alpha - 25-04-2022 */

does contain this problem.

@SyntaxRules @tivie