Being able to define the retryAfter

[mauriziovitale]

Is your feature request related to a problem? Please describe.
Being able to define the delay before retrying

Describe the solution you'd like
By configuring the action as follow
with:
result-encoding: string
retries: 3
retry-after: 500
script: |

By setting the retry-after the script to be called 3 time with a delay of 500 seconds in case of errors

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Expose the retryAfter option available on plugin-retry

[mauriziovitale]

Code pushed #355