Add directional position utilities

[Sebastian Nitu]

Problem

With the addition of the position utilities, there's a need to be able to set their top, right, bottom and left positions using utilities as well. The most basic example would be to set those values to 0. So we can use the following and not need additional CSS:

Example

<div class="position-sticky top">...</div>

Would be equivalent to

.selector {
  position: sticky;
  top: 0;
}