Create pattern for "occupational exposure"

[matentzn]

We need a pattern for "occupational exposure". for example, we need the following terms:

Occupational fume exposure
Occupational grain dust exposure
Occupational exposure to urea-based herbicide
Occupational exposure to organophosphorus herbicide
Occupational exposure to nitrile herbicide

And we should construct them from "Occupational exposure" and "fume exposure".

This is not the same as https://github.com/EnvironmentOntology/environmental-exposure-ontology/blob/master/src/patterns/dosdp-patterns/exposure_to_occupation.yaml

@rays22, can you create a suitable pattern and make a PR?

[rays22]

@rays22, can you create a suitable pattern and make a PR?

@matentzn , I have added a new occupational_exposure_to_material pattern in #252 .