Add basic string addition method

[AmeyaVS]

Add a basic class method test_strings_addition_with_params to TestStringMethods.

Also, adds test dependencies to pytest_discover_tests to following pytest sources:

• test/01-modify-name/strings/test_string_methods.py
• test/01-modify-name/test_math_operations.py

Any updates to these sources will trigger CMake to update *_test.cmake to be updated.
And this will keep development environment in sync with test sources updates.

Possible documentation update for the issue #50.

[buddly27]

This does not really demonstrate the issue of rebuilding the target when Python files are updated, so I would prefer not to add unnecessary tests. I think updating the documentation should be enough. Let me know what you think!

[AmeyaVS]

I appreciate the documentation update in #52 .
I know this PR is not really adding any new value, but it was for demonstrating limitations I faced while using this package on a bigger project.

[buddly27]

I understand, thank you for pointing out this issue!