add example to get result of sudo extrinsic

[dvc94ch]

runtime returns success for the sudo call even if the wrapped extrinsic fails. would be nice to have an example of how to get the result of the wrapped extrinsic.

for an example that reads the sudoid event to get the wrapped result in polkadotjs see:

• [0] https://polkadot.js.org/docs/api/cookbook/tx/