support `c8 ignore start`, `c8 ignore stop`

[connorjclark]

Since ignore AST nodes isn't an option, ignoring functions becomes difficult:

/* c8 ignore next 11 */
function wrapRuntimeEvalErrorInBrowser(err) {
  err = err || new Error();
  const fallbackMessage = typeof err === 'string' ? err : 'unknown error';

  return {
    __failedInBrowser: true,
    name: err.name || 'Error',
    message: err.message || fallbackMessage,
    stack: err.stack || (new Error()).stack,
  };
}

Most changes to this function will require modifying the ignore comment.

With istanbul it's trivial:

/* istanbul ignore next */
function wrapRuntimeEvalErrorInBrowser(err) {
  err = err || new Error();
  const fallbackMessage = typeof err === 'string' ? err : 'unknown error';

  return {
    __failedInBrowser: true,
    name: err.name || 'Error',
    message: err.message || fallbackMessage,
    stack: err.stack || (new Error()).stack,
  };
}

But no AST. instead, what about a "start ignoring" & "stop ignoring" comment?

[bcoe]

@connorjclark this seems like a reasonable compromise on not being able to ignore specific Node types.

I've been hesitant to want to introduce a JavaScript parser to the codebase.