Fixed the toggling behaviour in toggleLinks.

[pschijven]

This pull request fixes a small issue in the toggleLinks method.

Suppose I have selected the text uri and then press Cmd+K to create a link. Then the text [uri](https://) will be generated. If I press Cmd+K again, it currently reverts the text back to [uri instead of uri.

I have made a small correction to the regular expression in the toggleLinks method to fix this problem.

[erossini]

I saw your code. Thank you, it fixed my issue. If you like, here the full code https://github.com/erossini/EasyMarkdownEditor

[pschijven]

I saw your code. Thank you, it fixed my issue. If you like, here the full code https://github.com/erossini/EasyMarkdownEditor

I'm glad that I could be of help 👍