add shading to table component

lib/cannery_web/components/table_component.html.heex

@@ -33,8 +33,8 @@
       </tr>
     </thead>
     <tbody>
-      <%= for values <- @rows do %>
-        <tr>
+      <%= for {values, i} <- @rows |> Enum.with_index() do %>
+        <tr class={if i |> Integer.is_even(), do: @row_class, else: @alternate_row_class}>
           <%= for %{key: key} = value <- @columns do %>
             <td class={"p-2 #{value[:class]}"}>
               <%= case values |> Map.get(key) do %>