More RESTful style endpoints #115

In #106 @Bluenix2 suggested the below. I really like this proposed change, so I think we should do it after 106 is merged.

I am not sure how thoroughly this has been discussed, and how much of a say I have in this. But I have some opinions on the new endpoints, you currently have:

GET /size: Get the size of the canvas
GET /pixels: Get the whole canvas
GET /pixel: Get a specific pixel
PUT /pixel: Set a specific pixel
One quick thing I want to mention about /pixels, it doesn't really make sense, we're already at pixels.pythondiscord.com. Making the URL pixels.pythondiscord.com/pixels..

In my opinion, the following seem more RESTful:

GET /canvas/size: Get the size of the canvas alternatively this info could be included in the headers and would be mainly requested using HEAD /canvas.
GET /canvas: Get the whole canvas
alternatively the following two endpoints could use /canvas/pixels
GET /canvas?x=x&y=y: Get a specific pixel
PUT /canvas: Set a specific pixel you could also use query parameters here and the body would only consist of the color