feat: add comparison function for Duration

`compare/2` function to the Duration module, allowing for the comparison of two
Duration. The function returns `0`, `-1`, or `1` based on the equality and
relative values of the durations.

Author: yordis

lib/elixir/lib/calendar/duration.ex

@@ -299,6 +299,34 @@ defmodule Duration do
     }
   end
 
+  @doc """
+  Compares two durations.
+
+  Returns `:eq` if the durations are equal, `:lt` if the first duration is less than the second, and `:gt` if the first
+  duration is greater than the second.
+
+  ## Examples
+
+      iex> Duration.compare(Duration.new!(second: 10), Duration.new!(second: 20))
+      :lt
+      iex> Duration.compare(Duration.new!(second: 20), Duration.new!(second: 10))
+      :gt
+      iex> Duration.compare(Duration.new!(second: 10), Duration.new!(second: 10))
+      :eq
+  """
+  @doc since: "1.19.0"
+  @spec compare(t, t) :: :eq | :lt | :gt
+  def compare(%Duration{} = d1, %Duration{} = d2) do
+    d1_timeout = Kernel.to_timeout(d1)
+    d2_timeout = Kernel.to_timeout(d2)
+
+    cond do
+      d1_timeout == d2_timeout -> :eq
+      d1_timeout < d2_timeout -> :lt
+      d1_timeout > d2_timeout -> :gt
+    end
+  end
+
   @doc """
   Parses an [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601#Durations) formatted duration string to a `Duration` struct.