Write Vault and Stake Contracts

The library can be integrated seamlessly into your development environment to allow cross-chain transfer sequencing.
Refer to its integration into our sample Cross Chain Staking project as we move ahead. It consists of two contracts: Vault and Stake.
Vault contract enables the user to first transfer his funds from chain A to chain B and then stake them on chain B. This is the contract where we shall integrate our Sequencer Crosstalk library.
Stake contract just manages the staked tokens balance on the destination side.