Add support for named placeholders in custom task

mohzah commented 2 years ago

'custom' tasks can have named placeholders to be applied to the 'command' Issue: https://github.com/Azure/batch-shipyard/issues/374

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ghost commented 2 years ago

All CLA requirements met.

mohzah commented 2 years ago

@alfpark Can you please take a look?

Azure / batch-shipyard