Missing dependency on Starlette

[synapticarbors]

fastapi-mail has an explicit dependency on starlette that is missing in the pyproject.toml. It probably doesn't show up often because people are usually installing this package alongside fastapi, which pulls it in, but I noticed when I was packaging this package for conda-forge and building the package in isolation.

[sabuhish]

You are totally right, I have missed this. I was also using it without fastapi, I will take care of it today, thanks for pointing on it