Establish a standard way for *users* to provide additional metadata to the crate

[elichad]

Currently we have this way for a user to add their own metadata:

flwrCrate/flwrcrate/tracker.py

Lines 7 to 12 in cc44055

	with FLCrateTracker(
	context, strategy,
	output_dir="fl_crate_out",
	author="Ali",
	license="https://spdx.org/licenses/MIT.html",
	) as tracker:

We could also add reusable metadata to the pyproject.toml.