Interface to read PyCBC population file

For generating the population files, we decided not to implement any population model at this stage. Instead, we will use the existing PyCBC code to generate the population files. We need to write the code that reads and uses the PyCBC-generated files.

Expected outputs:

• A markdown file in docs/ to explain how to run PyCBC to obtain a population file
• A function in src/gwsim/utils/population.py to read the PyCBC file that returns a pandas DataFrame instance.

def read_pycbc_population_file(file_name: Path | str) -> pd.DataFrame:
    ...