add imports to mmm module (#812)

Co-authored-by: Juan Orduz <juanitorduz@gmail.com>

Author: williambdean

pymc_marketing/mmm/__init__.py

@@ -18,6 +18,8 @@
     DelayedAdstock,
     GeometricAdstock,
     WeibullAdstock,
+    WeibullCDFAdstock,
+    WeibullPDFAdstock,
 )
 from pymc_marketing.mmm.components.saturation import (
     HillSaturation,
@@ -51,6 +53,8 @@
     "TanhSaturation",
     "TanhSaturationBaselined",
     "WeibullAdstock",
+    "WeibullCDFAdstock",
+    "WeibullPDFAdstock",
     "YearlyFourier",
     "base",
     "delayed_saturated_mmm",