Default shiftKey behavior on transformer

[pro-nav]

I am working on a project where I need the default behavior of transformer to keep proportions while scaling. To achieve this, I am using the transformer({ keepRatio: true }). But now in some cases I want users to allow disregarding the proportions when the shift key is held during the transform. But the current behavior of transformer doesn't make this possible.

Ideally there should be a variable to something like shiftBehavior which can be default, inverted or none depending on which the value of the variable keepProportions is calculated.

var keepProportions;
switch(this.shiftBehavior){
    case 'inverted':
        keepProportions = this.keepRatio() && !e.shiftKey;
    case 'none':
        keepProportions = this.keepRatio();
    default:
        keepProportions = this.keepRatio() || e.shiftKey;
        break;
}

konva/src/shapes/Transformer.ts

Line 709 in 578191d

var keepProportion = this.keepRatio() || e.shiftKey;

[lavrton]

Do you want to make a Pull request?