Add rendering documentation

[dchirst]

What I am changing

• To add documentation about the rendering options for Titiler

How I did it

• I added sections for color mapping (default and custom), color formulae, and rescaling.

How you can test it

Related Issues

• add more documentation about rendering options #507

[dchirst]

This is a first draft, and there definitely could be improvements! Please let me know if there's something I should add

[vincentsarago]

🤯 Thanks so much @dchirst this is really great.

This was almost perfect 😄, just a quick not on the rescaling side, let me know if I make sense 🙏

[dchirst]

🤯 Thanks so much @dchirst this is really great.

This was almost perfect 😄, just a quick not on the rescaling side, let me know if I make sense 🙏

Fabulous, thanks so much! I'll get right on that change.

I also saw that you added rescaling dependency, so I'll add a reference to that in the docs

[dchirst]

I've made your suggested edits. Have a look to make sure it makes more sense!

I also considered adding the default colormap image from rio-tiler's docs, but thought that might be overcomplicating (especially if they update the default colormap list in the future). I can add it if you think it'd be a good idea