Proposal: Add unit abbreviations to unit.jsonld

[6d77]

In practical use units are often denoted by short identifiers, e.g. V for Volt. These are often used when a value has to be displayed or otherwise represented to a user.

I propose to add such short identifiers to each unit.

[akeranen]

Short, and in particular and consistent, unit identifiers make lots of sense. For SenML we had similar challenge and we established an IANA registry for them: https://www.iana.org/assignments/senml/senml.xhtml#senml-units

This registry can be easily extended so that is one viable option.