no_std support?

[MabezDev]

Just a brief skim of the code, it looks like the default formatting (no features enabled) doesn't use alloc or any std specific features?

Could this crate be used in a no_std environment with a bit of refactoring?

Edit: I missed the actual Format function :D - it looks like this only allocates to have a buffer to write into, perhaps there could be an alternative API that allows a slice to be passed instead.