added error message text to exploring_explorer (#1040)

notebooks/exploring_explorer.livemd

@@ -484,6 +484,8 @@ s1 = Series.from_list(["a", "b", "c"])
 Series.add(s, s1)
 ```
 
+> cannot invoke Explorer.Series.add/2 with mismatched dtypes: {:s, 64} and :string
+
 You can flip them around.
 
 ```elixir
@@ -968,6 +970,8 @@ Remember those helpful error messages?
 DF.filter(df, cuontry == "BRAZIL")
 ```
 
+> could not find column name "cuontry". Did you mean: "country"
+
 ### Mutate
 
 A common task in data analysis is to add columns or change existing ones. Mutate is a handy verb.
@@ -1526,6 +1530,8 @@ Trying for those helpful error messages again.
 DF.sample(df, 10000)
 ```
 
+> in order to sample more rows than are in the dataframe (1094), sampling `replace` must be true
+
 ```elixir
 DF.sample(df, 10000, replace: true)
 ```