function StateCore(instance, str, env) {
  this.src = str;
  this.env = env;
  this.options = instance.options;
  this.tokens = [];
  this.inlineMode = false;

  this.inline = instance.inline;
  this.block = instance.block;
  this.renderer = instance.renderer;
  this.typographer = instance.typographer;
}
The `StateCore` class manages state.

@param {Object} `instance` Remarkable instance
@param {String} `str` Markdown string
@param {Object} `env`