Add example on how to generate transaction IDs on demand and scenarios

[petreze]

Description:
Add example on how to generate transaction IDs on demand and two scenarios where this approach is useful
Scenarios:

Scenario 1:
Sometimes, when you are trying to execute transactions `asynchronosly`,
there is a tiny bit of chance to generate the same `transactionId` given the same `accountId`
and the current timestamp.
With the following approach to generate custom `transactionId`, this issue is avoided

Scenario 2:
The `TransactionId` object contains the valid start time for the transaction. This means that
by setting the valid start time to a moment in the future, you would be able to execute the transaction
after the set period (in seconds)

Related issue(s):

Fixes #1319

Notes for reviewer:

Checklist

• Documented (Code comments, README, etc.)
• Tested (unit, integration, etc.)

[sonarcloud]

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