ENH: Add Keywords parameter to make_dataset_description()

[bruAristimunha]

Describe the problem

make_dataset_description() accepts a fixed set of keyword arguments (name, authors, doi, funding, acknowledgements, etc.) but does not support Keywords, which is a valid BIDS field in dataset_description.json. Users who want to include keywords must manually patch the JSON after calling make_dataset_description().

Related: #302

Describe your solution

Add a keywords parameter to make_dataset_description():

def make_dataset_description(
    path,
    name=None,
    ...,
    keywords=None,  # NEW: list of str
    ...,
):

When provided, keywords should be written as the "Keywords" field in dataset_description.json.

Describe possible alternatives

1. Manual JSON patching (current workaround) — read, modify, write the JSON after make_dataset_description().
2. Only add extra_fields — a single generic parameter instead of explicitly adding keywords.

Current downstream workaround (MOABB)

mne_bids.make_dataset_description(path=str(root), overwrite=True, **desc_kwargs)

# Then patch in Keywords manually
desc_path = Path(root) / "dataset_description.json"
with open(desc_path) as f:
    desc = json.load(f)
if keywords and "Keywords" not in desc:
    desc["Keywords"] = keywords
    with open(desc_path, "w") as f:
        json.dump(desc, f, indent="\t")

Additional context

• Keywords is defined in the BIDS specification: https://bids-specification.readthedocs.io/en/stable/modality-agnostic-files.html#dataset-description
• mne-bids version: 0.19.0.dev
• Discovered while building BIDS export in MOABB and eegdash
• Originally discussed at ENH: Add Keywords parameter to make_dataset_description() bruAristimunha/mne-bids#15 with feedback from @drammock