feat(Grants): Implement Nodl Grants on ZkSync

[aliXsed]

Implement this contract to present similar but improved logic compared with pallet-grants on Eden parachain. Here is a couple of differences:

1. No admin or high level access is required. In pallet-grants the governance could cancel grants for anyone (not renounced) but this was too much unwarranted power. This contract allows any vesters to cancel their unvested grants if they have not renounced this authority towards a specific address.
2. Instead of unfriendly block numbers, here we use time stamps.
3. This contract would work with any standard Erc20 token and not just Nodl.

• Add more tests to cover all the errors and events.
• Add docs