feat(event listener): introduce BeforeJobRunsSkipIfBeforeFuncErrors as a new Eventlistener

[FalcoSuessgott]

What does this do?

This PR adds a new EventListener BeforeJobRunsSkipIfBeforeFuncErrors that exits job execution if the provided func returns an error

Use Case:
Im using gocron as a command wrapper for terraform to perform synthetic monitoring checks and came up with a configuration as follows:

settings:
  interval: 10s
  extra_labels:
    development: true

tests:
  vmware_vm:
    env:
      TF_VAR_content: "This is a variable"

    before_script:
      - cmd: terraform init
        retries: 2

    script:
      - cmd: terraform apply -auto-approve

    after_script:
      - cmd: terraform destroy -auto-approve

Where as the commands specified in the before_script block would be passed to BeforeJobRuns(), without this PR there was no way to stop the currents jobs execution in case of an error in any of the commands in before_script.

Introducing BeforeJobRunsSkipIfBeforeFuncErrors allows me to exit the jobs execution gracefully and reschedule to job after the given interval.

List any changes that modify/break current functionality

none

Have you included tests for your changes?

Si

Did you document any new/modified functionality?

• Updated example_test.go
• Updated README.md

Notes

[JohnRoesler]

Last thing, can you add an example to the example test file?

[JohnRoesler]

Nice!