openTab (filePath, options = {}, selected = true) {
    // TODO: Don't allow new files if quitting.
    if (this.lifecycle === WindowLifecycle.QUITTED) return
    this.openTabs([{ filePath, options, selected }])
  }
Open a new tab from a markdown file.

@param {string} filePath The markdown file path.
@param {string} [options] The tab option for the editor window.
@param {boolean} [selected] Whether the tab should become the selected tab (true if not set).