Add Morecantile as dependency?

[vincentsarago]

because @kylebarron loves mono-repo we could add morecantile as an optional dependency and archive rio-tiler-crs.

To make sure we keep compatibily, we will need to create an Object for mercantile that replicates morecantile methods.

This shouldn't be a breaking changes.

[vincentsarago]

I've started the implementation over #285

The more I think about it the more I think it will be OK to switch to morecantile directly 😄

Pro

• multiple TMS by default
• make rio-tiler-crs useless

Cons

• add a dependencies (morecantile needs pydantic)
• morecantile rely on TMS document while mercantile rely on pure maths (could be a pro 🤷‍♂️)

let's count the 👍 👎 please