Add Catmandu bind `maybe`

In order to not crash the whole transformation when using #698  `import` (not implemented yet) we also should introduce the `maybe` bind from Catmandu, so it only processes if the function within the bind are successful.

Example from Catmandu:

```
do maybe()
  my_fix1()
  my_fix2()
  download_from_internet() 
  process_results() # <--- this is skipped when download_from_internet fails
end
``