_setRouteContainer() {
    const body = document.getElementsByTagName("body")[0];
    let routeContainerEl = this.routeContainerEl = document.querySelector(this.config.routeContainer);
    if (!routeContainerEl) {
      const tempContainer = document.createElement("div");
      tempContainer.setAttribute("id", this.config.routeContainer.replace("#", ""));
      body.append(tempContainer);
      routeContainerEl = this.routeContainerEl = document.querySelector(this.config.routeContainer);
    }
  }
Save a reference to, and create if necessary, the HTML element to hold routes