create a global "please sign tx in your wallet" modal

[sirpy]

• based on usedapp notifications
• when a tx is in the waiting for sig state show a modal
• once a tx is in pending state you can then trigger the toast for txs

[L03TJ3]

@decentralauren not sure what to do with this or how to give it a 'priority-level'.
This is about what was discussed for user-feedback on gooddapp (including toasts).
and a more general implementation of transaction modals.

1. this only relates to anything that has been build since celo-launch (claim flow / buy-gd / microbridge)
2. nothing from any old(er) features can benefit from this
3. currently we only have the claim-flow live and already has a sign-tx modal in the flow

[decentralauren]

@L03TJ3 OK so the only benefit to implementing toasts now is for the claim flow to have a pending confirmation after the transaction is signed? Doesn't seem useful at this time, though adding toasts in the future may be appropriate.