Add placeholders to the searchbars in the Project/Editor settings

(cherry picked from commit 626d9d5ae4b21c0bd2b14f70b1048c4e1976669c)

editor/project_settings_editor.cpp

@@ -1843,6 +1843,7 @@ ProjectSettingsEditor::ProjectSettingsEditor(EditorData *p_data) {
 	search_bar->hide();
 
 	search_box = memnew(LineEdit);
+	search_box->set_placeholder(TTR("Search"));
 	search_box->set_h_size_flags(Control::SIZE_EXPAND_FILL);
 	search_bar->add_child(search_box);
 

editor/settings_config_dialog.cpp

@@ -426,6 +426,7 @@ EditorSettingsDialog::EditorSettingsDialog() {
 	tab_general->add_child(hbc);
 
 	search_box = memnew(LineEdit);
+	search_box->set_placeholder(TTR("Search"));
 	search_box->set_h_size_flags(Control::SIZE_EXPAND_FILL);
 	hbc->add_child(search_box);
 
@@ -469,6 +470,7 @@ EditorSettingsDialog::EditorSettingsDialog() {
 	tab_shortcuts->add_child(hbc);
 
 	shortcut_search_box = memnew(LineEdit);
+	shortcut_search_box->set_placeholder(TTR("Search"));
 	shortcut_search_box->set_h_size_flags(Control::SIZE_EXPAND_FILL);
 	hbc->add_child(shortcut_search_box);
 	shortcut_search_box->connect("text_changed", this, "_filter_shortcuts");