Allow the optional parameter when calling the task

[DjinNO]

Description

I have a set of included tasks:

includes:
  custom: 
    taskfile: ./t.custom.yml
    flatten: true
    optional: true

I would like to be able to specify that this task is optional when it is called
Either they must be optional by default, since include is optional

  name:
    cmds:
      - task: taskname
        optional: true

Now I have an error:

task: Task "taskname" does not exist