fix(modal): fix scrollbar compensation in some scaling situations (#3498)
fix(modal): fix scrollbar compensation in some scaling situations (#3498)

Now the actual width of the scrollbar is used to detect if it is present or not, instead of using the wrong hypothesis that if body's rect's width is smaller than viewport's width then there is a scrollbar. Now the difference in width is compared to the width of the scrollbar.

Adding uncertainty, because the scaling can make the gap just slightly smaller than a scrollbar size.

Closes #3448

maxokorokov/core,jnizet/ng-bootstrap,benouat/ng-bootstrap,maxokorokov/core,ng-bootstrap/ng-bootstrap,fbasso/ng-bootstrap,jnizet/ng-bootstrap,fbasso/ng-bootstrap,maxokorokov/core,benouat/ng-bootstrap,fbasso/ng-bootstrap,ng-bootstrap/ng-bootstrap,maxokorokov/core,jnizet/ng-bootstrap,jnizet/ng-bootstrap,ng-bootstrap/ng-bootstrap,ng-bootstrap/ng-bootstrap,benouat/ng-bootstrap,fbasso/ng-bootstrap,benouat/ng-bootstrap