Add new helper for request param matching on a regEx

[mcarti]

New Issue Checklist

• I have tried with the latest version of OHHTTPStubs
• I have read the README
• I have read the Using the right Swift Version of OHHTTPStubs for your project section
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Environment

• version of OHHTTPStubs: 8.0.0
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Issue Description

Not an issue but a proposition of a new helper. I use your library for testing my project and I thank you very much, it's very usefull.
For our project needs I've written a new helper I called 'containsQueryParamsMatching'. Whereas the existing helper 'containsQueryParams' matches on query parameter string value equality, 'containsQueryParamsMatching' matches on query parameter matching a given RegEx.
I'm ready to make a PR if you think this helper is usefull.

[jeffctown]

@mcarti - yes, a PR would be great!