[ENH] Add dicm2nii

[michellewang]

• [ ] Need to change defaults for outfmt to numbers + 'bids' because otherwise string escaping messes things up
• [ ] Invocation file needs paths to sub/ses folder

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.64%. Comparing base (fc3971f) to head (07a6778).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #270 +/- ## ======================================= Coverage 98.64% 98.64% ======================================= Files 28 28 Lines 1766 1766 ======================================= Hits 1742 1742 Misses 24 24 ```

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