Implement simple staking functionality

[0x-r4bbit]

With the list of available vaults implemented in #4 , we can now add a simple UI component that allows users to select a vault and enter a stake amount to stake in the protocol.

Another thing we can do is rendering the current stake amount of the selected vault.
Next to the stake amount, we probably also want to show MP (XP comes later)

Staking into a vault should update the UI accordingly.