[3.1.0] - 2023-02-18 added: * added feature flag `time`: Implements `Instant` for `time::Instant`. * added feature flag `coarsetime`: Implements `Instant` for `coarsetime::Instant`. * added `TimeSw` type alias to `StopwatchImpl<time::Instant>` * added `CoarseSw` type alias to `StopwatchImpl<coarsetime::Instant>` * added `SystemSw` type alias to `StopwatchImpl<std::time::SystemTime>` * added `StopwatchImpl::checked_toggle` * added `StopwatchImpl::checked_toggle_at` * added documentation notes about overflow to `StopwatchImpl::toggle` and `StopwatchImpl::toggle_at` changed: * changed overloaded `StopwatchImpl` addition and subtraction to panic on overflow