feat: smart contract verification

[janmichek]

Description

resolves #253

Demo

Checklist:

• [x] I have read and followed the Contributing Guide
• [x] add verification form

[github-actions[bot]]

Deployed to https://pr-636-aescan.stg.service.aepps.com

[janmichek]

I finished the feature @michele-franchi

• It cannot be tested as it relies on local docker instance
• the multi-contract has not been tested - I need to develop some small local app using SDK to deploy such contracts
• terms of service probably require update