Fix/contracts dependencies

[0x3bfc]

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[kremalicious]

haha, thanks, you were quick :-)

[kremalicious]

just a sec: not clear this is the right solution. It all depends on if the library should handle loading the correct artifacts so the frontends doesn't have to, or not

The current example tells developers to source the artifacts individually: https://github.com/oceanprotocol/ocean-lib-js/blob/develop/docs/README_marketplace_flow.md#2-alice-publishes-assets-for-data-services--publishes-a-datatoken-contract

This would imply users have to install @oceanprotocol/contracts on their own. If so, then they should be a peerDependency so devs are warned to install them on their own.

If the library should load the artifacts on its own, then @oceanprotocol/contracts can stay as proposed in this PR

[alexcos20]

the libary should handle the artifacts, at least by having some default ones.
If a dev wants to extend it or work with another version of the contracts, then he/she should be able to do that