feat: implement loadImage function

[twlite]

This PR implements the loadImage function, similar to node-canvas's loadImage.

It should support following sources:

• Buffer
• Image instance
• data uri
• remote url
• file path/url

API

import { loadImage } from "@napi-rs/canvas"

const image = await loadImage("...")
ctx.drawImage(image, ...)

[Brooooooklyn]

Thank you!