Add tests for WB custom regex module

[valearna]

In the new project structure, the WB custom regex class takes entities as arguments instead of reading them through wbtools. We need to create unit tests for this module by passing a small predefined list of entities and sentences containing genomic info taken from WB.

[rishabgit]

@valearna Added the tests, but they don't work - https://github.com/rishabgit/genomic-info-from-papers/blob/packaging/tests/entity_extraction/regex/wb_custom.py They do work fine in notebook using the predefined list of entities in the test file ^ Didn't get to look into why, let me know if you'd like me to

[valearna]

I fixed the regex extractor class and some minor issues with the tests and now everything looks good to me. @rishabgit please take a look at the changes and let me know if they are ok.

[rishabgit]

Looks good! 😀 I'll add specific test cases later