Update pvlib/atmosphere.py

Co-authored-by: Kevin Anderson <[email protected]>

Author: kurt-rhee

pvlib/atmosphere.py

@@ -385,6 +385,9 @@ def tdew_from_rh(
         Air temperature (dry-bulb temperature) in degrees Celsius
     relative_humidity : numeric
         Relative humidity as percentage (0-100)
+    coeff: tuple, default (6.112, 17.62, 243.12)
+        Magnus equation coefficients (A, B, C).  The default values are those
+        recommended by the WMO [1]_.
 
     Returns
     -------