add image buton

src/mechanize/form.cr

@@ -72,6 +72,8 @@ class MechanizeCr::Form
         buttons << FormContent::SubmitButton.new(html_node, @node)
       when"reset"
         buttons << FormContent::ResetButton.new(html_node, @node)
+      when "image"
+        buttons << FormContent::ImageButton.new(html_node, @node)
       when "text"
         fields << FormContent::Text.new(html_node)
       when "hidden"

src/mechanize/form/button.cr

@@ -7,3 +7,4 @@ class MechanizeCr::FormContent::Button < MechanizeCr::FormContent::Field
 end
 require "./reset_button"
 require "./submit_button"
+require "./image_button"

src/mechanize/form/image_button.cr

@@ -0,0 +1,2 @@
+class MechanizeCr::FormContent::ImageButton < MechanizeCr::FormContent::Button
+end