Add walls to the right and left of the canvas

[krowter]

Description

Tetris game usually have "walls" on the right and left to prevent the shapes from going beyond the game. Currently this repo doesn't have that.

Existing

If a user keeps pressing arrow right, the shape will keep moving to the right until if disappears from canvas view.

Expected

If a user keeps pressing arrow right, the shape will move to the right until it collides with the side of canvas only, no further.

Task

In the event listened inside createShape() add if statement to prevent the increment/decrement of positionX if it goes below 0 or above the canvas width.