add section in README-SEMANTICS about API calls and model ops (#59)
add section in README-SEMANTICS about API calls and model ops (#59)

Co-authored-by: Sam Thomson <5229dd6eb26cf988c0b8ab17c1252fb93839309b@microsoft.com>
microsoft/task_oriented_dialogue_as_dataflow_synthesis,microsoft/task_oriented_dialogue_as_dataflow_synthesis