[ENH] Write QC report generation DAG for BIDS data

[jerdra]

This DAG will generate QC images (.svg/.png) from data present in a given BIDS folder produced by the XNAT extract step.

• [ ] Integrate Niviz as an air-tigrs dependency
• [ ] Set up Niviz specification for producing QC images from BIDS folder
• [ ] Write DAG to produce QC images