Applications: Use modeless windows in some apps

Browser, Spreadsheet and Charactermap now open child windows
modelessly.

Userland/Applications/Browser/Tab.cpp

@@ -79,6 +79,7 @@ void Tab::view_source(const URL& url, String const& source)
     window->resize(640, 480);
     window->set_title(url.to_string());
     window->set_icon(g_icon_bag.filetype_text);
+    window->set_window_mode(GUI::WindowMode::Modeless);
     window->show();
 }
 
@@ -555,6 +556,7 @@ void Tab::show_inspector_window(Browser::Tab::InspectorTarget inspector_target)
 {
     if (!m_dom_inspector_widget) {
         auto window = GUI::Window::construct(&this->window());
+        window->set_window_mode(GUI::WindowMode::Modeless);
         window->resize(300, 500);
         window->set_title("Inspector");
         window->set_icon(g_icon_bag.inspector_object);

Userland/Applications/CharacterMap/CharacterMapWidget.cpp

@@ -94,6 +94,7 @@ CharacterMapWidget::CharacterMapWidget()
             m_find_window->set_icon(GUI::Icon::try_create_default_icon("find"sv).value().bitmap_for_size(16));
             m_find_window->set_title("Find a character");
             m_find_window->resize(300, 400);
+            m_find_window->set_window_mode(GUI::WindowMode::Modeless);
         }
         m_find_window->show();
         m_find_window->move_to_front();

Userland/Applications/Spreadsheet/SpreadsheetWidget.cpp

@@ -53,6 +53,7 @@ SpreadsheetWidget::SpreadsheetWidget(GUI::Window& parent_window, NonnullRefPtrVe
             auto docs = sheet_ptr->gather_documentation();
             auto help_window = HelpWindow::the(window());
             help_window->set_docs(move(docs));
+            help_window->set_window_mode(GUI::WindowMode::Modeless);
             help_window->show();
         }
     };