SensorMode is not available

[vasilNnikolov]

I'm playing around with a BME280, and I have to say, this library is a great starting point. However, it seems (please correct me if I'm wrong) that the current public API does not expose the functions to set the sensor mode (sleep, forced, normal), despite it being used internally. From the current implementation of AsyncBME280Common::measure it seems all measurements are made in Forced mode.

I'd like to use Normal mode to have the IIR filtering and continuous data measurements. I will fork and start an MR when I have something working, meanwhile, all feedback on this is appreciated.