readYaml function
Reads the yamlFile and returns a map of its contents.
The yamlFile is passed as a File object instead of being hardcoded
because in the future, we may support reading multiple files for configuration.
Implementation
Map<String, dynamic> readYaml(File yamlFile) {
  final yamlMap = (loadYaml(yamlFile.readAsStringSync()) ?? YamlMap()) as Map;
  // yamlMap has the type YamlMap, which has several unwanted side effects
  var json = yamlToMap(yamlMap as YamlMap);
  return json;
}