[ENH] Add in dataladSetUp.sh ho to add code libraries as submod

### Is there an existing issue for this?

- [X] I have searched the existing issues

### New feature

```markdown
e.g.:

presurf_url='git@github.com:srikash/presurfer.git'
datalad install -d . -s "${presurf_url}" "${root_dir}"/code/lib/presurfer
```


### Unclear documentation

```markdown
Suggested by @jacmatu
```
