Consolidate development dependencies

[VeckoTheGecko]

Dependencies for the project are spread across a few different files

Production:

PyCO2SYS/pyproject.toml

Lines 7 to 14 in 437db5d

	[project]
	name = "PyCO2SYS"
	description = "PyCO2SYS: marine carbonate system calculations in Python"
	readme = "README.md"
	dependencies = [
	"jax",
	"networkx",
	]

Development/documentation:

PyCO2SYS/.github/workflows/python-package.yml

Lines 20 to 24 in 437db5d

	- name: Install dependencies
	run: |
	python -m pip install --upgrade pip
	pip install pytest xarray pandas openpyxl
	pip install .

PyCO2SYS/docs/requirements.txt

Line 1 in 437db5d

mkdocs-material

I suggest consolidating these dependencies into one development Conda environment file (environment.yml), that way documentation, testing, and local development can use all the same dev dependencies. Also makes it easier for new devs to get started.