chore: improved docstring for skdecimal

Author: xmatthias

freqtrade/optimize/space/decimalspace.py

@@ -6,12 +6,19 @@ def __init__(
         self,
         low: float,
         high: float,
+        *,
         step: float | None = None,
         decimals: int = 3,
         name=None,
     ):
         """
         FloatDistribution with a fixed step size.
+        Only one of step or decimals can be set.
+        :param low: lower bound
+        :param high: upper bound
+        :param step: step size (e.g. 0.001)
+        :param decimals: number of decimal places to round to (e.g. 3)
+        :param name: name of the distribution
         """
         if decimals is not None and step is not None:
             raise ValueError("You can only set one of decimals or step")