add tests

[BFalquet]

This pull request introduces an automated approach for generating test scaffolding for functions defined in Quarto catalog files, and adds a new snapshot test for the fda-table_* functions. The changes streamline the process of creating standardized tests, making it easier to maintain and extend test coverage for catalog functions.

Automated test generation:

• Added a new script, inst/create_tests.r, which scans Quarto catalog files for function definitions, extracts their code, and generates corresponding test files in tests/testthat using a template. This automates the creation of test scaffolding for each function, reducing manual effort and ensuring consistency.
• Introduced a test template in inst/template_test.R that standardizes the structure of generated tests, including snapshot testing for the function's output.

Testing improvements:

• Added a new snapshot test output for the fda-table_* functions in tests/testthat/_snaps/fda-table_*.md, capturing the expected structure and values of its summary and overall tables. This helps detect regressions in future changes.

thank you for the review

[shajoezhu]

This looks great! Thanks a lot @BFalquet