Clarify "detect and correct outliers" vignette

[nmdefries]

"Outliers" vignette

• RE "Detection based on rolling median", is a "residual" equal to the difference between rolling median and observations? Can we also use IQR on observations instead of residuals?
• In the reference for detect_outlr_stl(), the description for detection_multiplier should change to fitted value/residuals from STL instead of rolling median.
• The bands from the stl_seasonality method are much narrower than others. Verify that this one is also using majority vote to choose detection method.