Reduce the amount of dependencies

[josevalim]

Currently we depend on Req+Jason, and we can't compile those easily on Fly due to limited memory.

We could make both of those optional by hardcoding the style inside the library, which may be the plan with #17. Then if someone passes a URL or binary as style, we check if Req/Jason is available before continuing.

However, I think this can still be an issue with Kino.MapLibre, because we support multiple styles there by default, right? Maybe we should support only the default style and if someone wants to change it, they can change it in the code?

Thoughts?

Why not offer all 3 we support today as decoded json? Only one is quite limiting, especially for MapCell.

[josevalim]

Oh, maybe we can support the :style to be an atom and the atom will point to one of the hardcoded styles we have, like the three we use in the Kino?