Fix/post tx state

[jordaniza]

Adds a 2 way binding to the fetched wkpi balance and updates on submission of the transaction.

Works as follows:

• Instantiate the data fetch in the parent component
• Two way bind the data between parent and child
• Submit the transaction
• On success, the child component optimistically updates the bound balance of wKPI tokens
• On error, display the error message, do not update the state