DOC: Add wrapper usage

Author: mgxd

README.md

@@ -317,6 +317,27 @@ NiBabies specific options:
 
 </details>
 
+
+#### Running with ``nibabies-wrapper``
+
+The ``nibabies-wrapper`` is a lightweight Python 2/3 wrapper for running *NiBabies* via Docker and Singularity.
+It will generate a Docker/Singularity command line for you, print it out for reporting purposes, and then execute it without further action needed, e.g.:
+
+
+##### Docker
+```
+$ nibabies-wrapper docker /path/to/data /path/to/output participant --age-months 12
+RUNNING: docker run --rm -e DOCKER_VERSION_8395080871=20.10.6 -it -v /path/to/data:/data:ro \
+-v /path/to/output:/out nipreps/nibabies:0.1.1 /data /out participant --age-months 12
+```
+
+##### Singularity
+```
+$ nibabies-wrapper singularity /path/to/data /path/to/output participant --age-months 12 -i nibabies-0.1.1.sif
+RUNNING: singularity run --cleanenv -B /path/to/data:/data:ro \
+-B /path/to/output:/out nibabies-0.1.1.sif /data /out participant --age-months 12
+```
+
 ### Outputs
 
 TODO - Refer to [fMRIPrep's outputs](https://fmriprep.org/en/20.2.1/outputs.html) for now.