extend description of readme

Sorry but I am a bit confused about this repo. From the description I'd think is about creating a unique identifier for each instance of something in bonsai, (a taxonomy?) but I think it is more than that, because we are adding things like labels. Is like if we were defining (all? just the essential?) triplets related to a given instance. Is it because each triplet is a uri in itself?

I think it would be nice to add an example on the readme.

For example the ttl defining the [exiobase flow objects](https://github.com/BONSAMURAIS/rdf/blob/master/flowobject/exiobase3_3_17/exiobase3_3_17.ttl):

brdffo:C_ASHW a bont:FlowObject ;
brdffo:C_ASHW rdfs:label "Ash for treatment; Re-processing of ash into clinker" .

being
brdffo : http://rdf.bonsai.uno/flowobject/exiobase3_3_17/
and bont: http://ontology.bonsai.uno/core#

if "Ash for treatment; Re-processing of ash into clinker" turns out to be of part of particular product classification, would this also be stored in arborist? if so, could somebody give an example?

Start with the README and the linked flowobject/exiobase3_3_17/exiobase3_3_17.ttl example. Clarify the repository’s URI and triplet model using that example, including whether product-classification relationships belong in arborist; done when the README answers these questions with a concrete example.

Written by the indexing model from the issue text.