support data validation where source is within same sheet or reference to other sheet

example.exs

@@ -47,6 +47,10 @@ sheet1 = Sheet.with_name("First")
   |> Sheet.set_cell("A2", "cat")
   |> Sheet.set_cell("A3", "cow")
   |> Sheet.add_data_validations("A1", "A10", ["dog", "cat", "cow"])
+  # within same sheet
+  |> Sheet.add_data_validations("A1", "A10", "=$A$2:$A$16")
+  # reference to other sheet  "=#{sheet.name}!$A$2:$A$16"
+  |> Sheet.add_data_validations("A1", "A10", "=sheet2!$A$2:$A$16")
 
 workbook = %Workbook{sheets: [sheet1]}
 

lib/elixlsx/sheet.ex

@@ -41,7 +41,7 @@ defmodule Elixlsx.Sheet do
           merge_cells: [{String.t(), String.t()}],
           pane_freeze: {number, number} | nil,
           show_grid_lines: boolean(),
-          data_validations: list({String.t(), String.t(), list(String.t())})
+          data_validations: list({String.t(), String.t(), list(String.t()) | String.t()})
         }
   @type rowcol_group :: Range.t() | {Range.t(), opts :: keyword}
 

lib/elixlsx/xml_templates.ex

@@ -300,6 +300,16 @@ defmodule Elixlsx.XMLTemplates do
     """
   end
 
+  defp make_data_validation({start_cell, end_cell, values}) when is_bitstring(values) do
+    """
+    <dataValidation type="list" allowBlank="1" showErrorMessage="1" sqref="#{start_cell}:#{
+      end_cell
+    }">
+      <formula1>#{values}</formula1>
+    </dataValidation>
+    """
+  end
+
   defp make_data_validation({start_cell, end_cell, values}) do
     joined_values =
       values