Fix regex pattern for logical selection for is()/:where() with complex selectors containing :nth-child()

[jackboike]

Issue: #165

[dperini]

@jackboike
first of all I wanted to thank you for the efforts and the time you give contributing to our "nwsapi" project.

We recently reached the 20th year of the development and support we gave this project initially under the name of "nwmatcher" and since 2016 and later with th name "nwsapi".

It is thanks to many developers like you and lately to some contributors, sponsors and small donations that this
project will continue and improve.

I am working on the parser with multi-depth resolution capabilities, adding security configurations, helper setting limitations additions to complete the Selectors Level 4 support.

After pushing the commits that have sit in the queue for the last 3 months I will make sure to review your Regular Expression and see if it solves the problems you encountered in the current version using the sae test you attached.

Be patient, I am now 66 year old, slower than ever and with added disabilities.