Add "Advanced" action for actions not yet available in the drop down

[olanod]

We should include a way to paste the hex string of an extrinsic generated in PolkadotJs as a possible "advanced" action(the copy can change). In the future we can improve it showing the detail of the extrinsic and later it can become an "extrinsic builder" that allows users create new actions.

[ljuanto]

#142 (comment)