showHint method
Fast path for a single hint: a one-step tour without HintTour ceremony.
Equivalent to start(HintTour(id: 'hint:<targetId>', steps: [step])) —
the same wait-for-target, timeout, typo validation and diagnostics as a
full tour. One tour at a time: calling it during an active tour is an
assert (same as start).
Implementation
Future<void> showHint(HintStep step) => start(
HintTour(id: 'hint:${step.targetId}', steps: [step]),
);