fix: added model export to main module, subdirectory

[MrStLouis]

I have added a global export within the main index.ts file as well as adding the dist/models path to the files list in the package.json

This should allow users to import models from main

import Harvest, { Company, EstimateItemCategory } from 'harvest';
. . .

and if its just a model folder that does not require the client

import { Company, EstimateItemCategory } from 'harvest/dist/models';
. . .