Make the canvas resisable and add a gradient function

[rohittp0]

Is your feature request related to a problem? Please describe.
Joy can be used to make many detailed patterns, but currently, due to the small size of the canvas, it is very hard to present the created sketches without losing the details.
Currently, there is no easy way to create a gradient using Joy, but gradients are useful in making many designs.

Describe the solution you'd like
Add a text box ( or some UI element ) using which the user can set the size of the canvas.
add a transformation gradient(color1,color2,color3...) that adds the gradient to a given shape, gradient(color) can be used to just change the color of the shape.

[anandology]

@rohittp0 could you please split these into two separate issues? Let this issue be about resizing the canvas and please create a new issue for gradient.