add normal button

spec/form_spec.cr

@@ -24,6 +24,7 @@ WebMock.stub(:get, "example.com/check_form").to_return(body:
       <input type="reset" value="no">
       <input type="submit" value="submit">
       <input type="image" src="images/kaeru.png" alt="gerogero">
+      <button class="favorite styled" type="button">
     </form>
   </body>
 </html>
@@ -48,6 +49,6 @@ describe "Mechanize Form test" do
     form.fields.size.should eq 4
     form.checkboxes.size.should eq 1
     form.radiobuttons.size.should eq 3
-    form.buttons.size.should eq 4
+    form.buttons.size.should eq 5
   end
 end

src/mechanize/form.cr

@@ -91,6 +91,13 @@ class MechanizeCr::Form
       next if node["name"].empty?
       @fields << FormContent::Textarea.new(node, node.inner_text)
     end
+
+    @node.css("button").each do |node|
+      node = node.as(Myhtml::Node)
+      type = node.fetch("type", "submit").downcase
+      next if type == "reset"
+      @buttons << FormContent::Button.new(node, @node)
+    end
   end
 
   private def build_query_string(params : Array(Array(String)))