Feature suggestion: Warn user about insufficient funds

[Thegaram]

Conflux nodes will accept transactions, even if the sender is unable to cover the associated costs. In this case, the tx will be pending for a while then Studio will signal timeout. Some users might find this behavior surprising. I suggest Conflux Studio should check the user's balance at the time of sending the transaction, and give a warning like "Your current balance is not enough to cover this transaction, do you want to send it anyway?".