Absence of gantt-container check for existing

[ArtemOstapov]

If i use own react wrapper the gantt-container div created 2 times with corresponding inside divs.

Could you plz add for that code checks for existing it like with svg you have

// wrapper element
this.$container = document.createElement('div');
this.$container.classList.add('gantt-container');

to

// wrapper element
this.$container = document.querySelector('.gantt-container');

if (!this.$container) {
    this.$container = document.createElement('div');
    this.$container.classList.add('gantt-container');
}

and

// popup wrapper
this.popup_wrapper = document.createElement('div');
this.popup_wrapper.classList.add('popup-wrapper');
this.$container.appendChild(this.popup_wrapper);

to

 this.popup_wrapper = this.$container.querySelector('.popup-wrapper');

if (!this.popup_wrapper) {
    this.popup_wrapper = document.createElement('div');
    this.popup_wrapper.classList.add('popup-wrapper');
    this.$container.appendChild(this.popup_wrapper);
}