TypeScript typings for regl

• Test it in JavaScript project, as opposed to TypeScript project.
• Try createREGL in module-less, aka global environment.
• Add typings for regl.read().
• Support all ways to create/reinitialize a texture from arrays/typed arrays/ndarrays/framebuffers/textures. See https://github.com/regl-project/regl/blob/gh-pages/API.md#texture-constructor
• Add typings for regl.texture({ copy: true }).
• Add typings for REGL.Props.
• Maybe introduce nested namespaces, like REGL.Drawing and REGL.Texture to decrease top-level module clutter.
• Downgrade *Options from interfaces to object types.

In general, I see REGL.Command as a generic type parametrized by the type of its props, like so

interface MyCommandProps {
    color: [number, number, number, number];
}

const myCommand: REGL.Command<MyCommandProps> = regl({
    // ...
})

myCommand({
    colour: [1, 0, 0, 1], // This should err in compile time, because colour != color
}); 

React's component types are parametrized with the types of their props (and state, for stateful components). This allows for compile-time error checks regarding props' names and types, and that's a Good Thing.