- Update version to 1.26.0
* Translations update
* Replace the deprecated GtkTable with GtkGrid
* Replace the deprecated gtk_widget_set_state with gtk_widget_set_state_flags
* Remove useless and discarded gtk_button_released
* Replace the deprecated g_bookmark_file_get_modified with
g_bookmark_file_get_modified_date_time
* Fix compilation warning
* Use gtk-cancel icon replace window-close icon
* update copyright to 2021