Add more filters/smoothing

[kylecorry31]

• Savitzky-Golay
• Loess
• Median filter
• Linear regression
• Polynomial regression

See https://github.com/cerlymarco/tsmoothie

Loess
https://towardsdatascience.com/loess-373d43b03564
https://www.youtube.com/watch?v=Vf7oJ6z2LCc
https://www.youtube.com/watch?v=b7oryuMP3r8