feat: provide matches regex assertion for strings

[haraldmaida]

Implemented new assertion matches for strings. It verifies whether a string matches the given regex.

This assertion requires crate feature regex which is enabled by default.

[codecov]

Codecov Report

Attention: Patch coverage is 91.17647% with 3 lines in your changes missing coverage. Please review.

Project coverage is 93.71%. Comparing base (2fe5634) to head (23ab3b4).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/string/mod.rs	89.28%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #24      +/-   ##
==========================================
- Coverage   94.05%   93.71%   -0.34%     
==========================================
  Files          24       24              
  Lines        2272     2547     +275     
  Branches     2272     2547     +275     
==========================================
+ Hits         2137     2387     +250     
- Misses        129      153      +24     
- Partials        6        7       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.