Fix dynamic parameter regex replacement in `processComplexMatch`

[erikjuhani]

Hey again @wesleytodd! 👋

One test case was failing as mentioned in my other pr #64. This should fix that issue!

The replace failed to inject the route parameter as the layer regex was changed from /^\/(?:([^\/]+?))\/?(?=\/|$)/i to /^(?:\/([^/]+?))\/?(?=\/|$)/i.

Now both regex cases are taken into consideration. The regex was changed to use optional non-capturing groups for the differences between the two possible regex patterns.

Link to playground using the new regex format: https://regex101.com/r/cursDu/1