parentheses in anchor tags aren't escaped

[mmkal]

Example input:

<a href="https://en.wikipedia.org/wiki/Democratic_Party_(United_States)">Democratic Party</a>

Expected output

[Democratic Party](https://en.wikipedia.org/wiki/Democratic_Party_\(United_States\))

Actual output:

[Democratic Party](https://en.wikipedia.org/wiki/Democratic_Party_(United_States))

[mmkal]

(awesome lib, btw - I'm able to work around this issue and the other one I filed pretty easily with a custom rule but thought it was worth pointing out in case you want to put a fix in this package too)