DOC/PLT: Add stacked in doc and doc example for barh and bar plot (pandas-dev#33337)

Author: charlesdong1991

pandas/plotting/_core.py

@@ -1015,6 +1015,13 @@ def line(self, x=None, y=None, **kwargs):
             ...                    'lifespan': lifespan}, index=index)
             >>> ax = df.plot.bar(rot=0)
 
+        Plot stacked bar charts for the DataFrame
+
+        .. plot::
+            :context: close-figs
+
+            >>> ax = df.plot.bar(stacked=True)
+
         Instead of nesting, the figure can be split by column with
         ``subplots=True``. In this case, a :class:`numpy.ndarray` of
         :class:`matplotlib.axes.Axes` are returned.
@@ -1096,6 +1103,13 @@ def bar(self, x=None, y=None, **kwargs):
             ...                    'lifespan': lifespan}, index=index)
             >>> ax = df.plot.barh()
 
+        Plot stacked barh charts for the DataFrame
+
+        .. plot::
+            :context: close-figs
+
+            >>> ax = df.plot.barh(stacked=True)
+
         We can specify colors for each column
 
         .. plot::