add image to Dagster as asset metadata

asset.py

# For metadata
buffer = BytesIO()
_gd_diagram.write(buffer, "png")
image_data = base64.b64encode(buffer.getvalue())

# Asset metadata
context.add_output_metadata(
    metadata={
        "text_metadata": "A synteny diagram had been created.",
        "num_sqcs": len(_records),
        "path": _path_output,
        "sequences": MetadataValue.json(_record_names),
        "synteny_overview": MetadataValue.md(
            f"![img](data:image/png;base64,{image_data.decode()})"
        ),
    }
)