Check equality of markdown YAML header option

# S3 method for MarkdownYamlOptionState
check_equal(state,
  incorrect_msg = NULL, append = TRUE, ...)

Arguments

state	the state to start from. Should be a state produced by `check_option`.
incorrect_msg	If specified, this overrides the automatically generated message in case the options don't match between student and solution.
append	Whether or not to append the feedback to feedback built in previous states.
...	S3 stuff