Implement binding to create mutating hooks

[diafour]

Is your feature request related to a problem? Please describe.

Shell-operator supports only validating admission webhook. Mutating webhook is missing. More info.

Describe the solution you'd like to see

• Add new binding kubernetesMutating
• Design config for this hooks
• Add documentation for new binding
• Add example (mutate Pod to add sidecar container)

Describe alternatives you've considered

Additional context