text: Title: Linreg does not return Slope, Forecast, Angle, or R coefficient
  Body: Which version are you running?  0.3.14b0
  Do you have TA Lib also installed in your environment? No
  
  The LINREG indicator returns the linreg indicator value but does not return other useful indicator values mentioned in the documentation - e.g. Slope, Forecast, Angle, or R coefficient which are calculated in the indicator code.
  
  Sample code to reproduce:
  
  ```python
  import pandas as pd
  import pandas_ta as ta
  import yfinance as yf
  
  print(f"PANDAS TA version = {ta.version}")
  # Get symbol OHLC data
  data = yf.download("CL=F")
  
  # pandas_ta linreg doesn't appear to be returning all the values yet...
  
  # this works
  data['LINREG'] = data.ta.linreg(length=20, slope=True, degrees=True, r=True, tsf = True )
  
  # this (below) doesn't work as dictionary key values are missing
  # linreg = data.ta.linreg(length=20, slope=True, degrees=True, r=True, tsf = True ) 
  # data['LINREG'] =  linreg['LR_20']
  # data['LINREG_SLOPE'] = linreg['LRm_20']
  # data['LINREG_FORECAST'] = linreg['LR_20']
  # data['LINREG_ANGLE'] = linreg['LRa_20']
  # data['LINREG_R'] = linreg['LRr_20']
  ```
  
  Expected: indicator values described in the documentation (and calculated in the indicator code) should be available