add(value) {
    // add node using the regular BST add
    const node = super.add(value);

    if (node === this.root) {
      node.meta.color = BLACK;
    } else {
      node.meta.color = RED;
      this.balance(node);
    }

    return node;
  }
Insert node in the tree.

The root is always BLACK.
New nodes are always RED.

@param {any} value new nodes' value