Allow requirement file in hatch environment depenedencies

[ketozhang]

Description

Add feature to allow use of requirements file when specifying hatch environments.

[tool.hatch.envs.<env>.dependencies]
dependency-file = "requirements.txt"

Other Additional Information:

My use case is docs environment where I have to keep a separate requirements/docs.txt file for local build and CI build of docs. The CI is from RTD which only allows requirement files. I have other options which I'd like to not explore right now.