docs: restore Config.load/0 example using #=> notation

The previous iex> examples were removed because they would fail as
doctests once the module's doctest was activated. Restore the example
using a #=> comment so it's shown in generated docs without being
executed as a test.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: fahchen

lib/dprint_markdown_formatter/config.ex

@@ -77,6 +77,12 @@ defmodule DprintMarkdownFormatter.Config do
 
   Returns a validated configuration struct with proper type checking. Invalid
   values are replaced with defaults and warnings are logged.
+
+  ## Examples
+
+      # With valid configuration in mix.exs
+      DprintMarkdownFormatter.Config.load()
+      #=> %DprintMarkdownFormatter.Config{line_width: 80, text_wrap: :always}
   """
   @spec load() :: t()
   def load do