import contracts from their npm package

Feature Description

they should be in their own repo, versioned, exporting the json-artifacts including the addresses of the deployed testnet-instances. Whenever a new (breaking) version is pushed to that repo, prefixed with a keyword, the contracts should be redeployed.

Motivation and Context

so that othe projects can import them

Related Issues/Tasks

• move contracts to repo and npm package (see https://www.npmjs.com/package/fathom-contracts)
• import that package
• set up the repo to do automatic redeployment for new versions (could be its own issue)
• adjust tests/ CI-pipelines in both repos
• figure out where all the AHAs are on the kovan testnet

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