Apps/Feature #37: add onUserReject event handler

[mmv08]

This PR:

• Adds changes required for Feature #37: Add onTransactionRejection handler safe-global/safe-apps-sdk#47 and Add a listener for transaction rejection safe-global/safe-apps-sdk#37 to work by allowing to pass onUserReject handler to createTransaction action
• The transaction is assumed to be rejected by the user if the transaction error message has a User word in it. I tested it with multiple wallets and most of them seem to do that

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Type	Occurrences	Fixable
Errors	0	0
Warnings	0	0
Ignored	0	N/A

• Result: ✅ success
• Annotations: 0 total

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Travis automatic deployment:
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Travis automatic deployment:
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