### Summary

Add type hints to `ansible.parsing.dataloader::DataLoader`

### Issue Type

Feature Idea

### Component Name

lib/ansible/parsing/dataloader.py
'''
        find one file in first path in stack taking roles into account and adding play basedir as fallback
        :arg paths: A list of text strings which are the paths to look for the filename in.
        :arg dirname: A text string representing a directory.  The directory
            is prepended to the source to form the path to search for.
        :arg source: A text string which is the filename to search for
        :rtype: A text string
        :returns: An absolute path to the filename ``source`` if found
        :raises: An AnsibleFileNotFound Exception if the file is found to exist in the search paths
        '''
        b_dirname = to_bytes(dirname, errors='surrogate_or_strict')
        b_source = to_bytes(source, errors='surrogate_or_strict')
        result = None
        search = []
        if source is None:
            display.warning('Invalid request to find a file that matches a "null" value')
        elif source and (source.startswith('~') or source.startswith(os.path.sep)):
            
            test_path = unfrackpath(b_source, follow=False)
            if os.path.exists(to_bytes(test_path, errors='surrogate_or_strict')):
                result = test_path