Detect URL when clicking to activate URL

Makes the case where the screen contents have changed
between the last mouse move and the click work. See #1203

kitty/mouse.c

@@ -364,6 +364,7 @@ HANDLER(add_click) {
 static inline void
 open_url(Window *w) {
     Screen *screen = w->render_data.screen;
+    detect_url(screen, w->mouse_pos.cell_x, w->mouse_pos.cell_y);
     screen_open_url(screen);
 }