Add height option to SnapLikeCellSize

Changed property name of SnapLikeCellSize.

• normal → normalWidth
• center → centerWidth
• add normalHeight and centerHeight

Example

let cellSize = SnapLikeCellSize(normalWidth: 100, centerWidth: 160)

Or you can add height option like this.

let cellSize = SnapLikeCellSize(
    normalWidth: 100,
    centerWidth: 160,
    normalHeight: 200,
    centerHeight: 300
)