Do not let 0-size Dynamic element overlay others

[tomalec]

Currently 0 size elements, are being packed to 0,0 (as that's the first spot where they fit), so they are being placed in the same row/col as the first visible element.

The problem starts for dynamic 0-size elements.
Even if the element itself, is still 0 size, its juicy-tile in shadow DOM occupies entire grid cell, therefore it overlays other elements in this cell.

The size of a shadow juicy-tile, should be min-content so it will remain 0-size and do not overlay other items.
Then even if the element will grow, the dimension of the overlay will be equal to element's size.
Related issue: #18