Add example nirx recording using NIRStar 15.2 with short channels

[rob-luke]

Add NIRx recordings for new file reader proposed in MNE PR.

File Generation

1. Open NIRSite 2.0

2. Add sources at T7, TP8, P01, AF2, Cz

3. Add detectors at T8, TP7, P02, AF1, FC1, CP2, CP1. FC2

4. Add short channels to T7, TP8, P01, AF2, Cz
   The screen now looks like...
   
   

5. Save and selection option to target the NIRStar application. Check all boxes

6. Close NIRSite and open NIRStar 15.2

7. Go to Configure Hardware -> Montage -> and select the montage saved above

8. Leave other options as standard. Just in case here are screen shots of all other tabs
   
   
   
   

9. Exit hardware setup and click Calibrate
   

10. Record approximately 6s of data and save

[rob-luke]

Once your PR is merged, ask a maintainer to cut a new release of the testing data, e.g. 0.53.

@larsoner could you please take a look at this PR and let me know if I missed any steps and need to anything else.

[rob-luke]

I forgot to ensure their were triggers in the data. I will rerecord with a stimulus and re-upload.

[rob-luke]

Fixed version in #51