patch 8.1.1522: poup_notification() not implemented yet
Problem: Popup_notification() not implemented yet.
Solution: Implement it.
diff --git a/src/proto/popupwin.pro b/src/proto/popupwin.pro
index a274446..03d3729 100644
--- a/src/proto/popupwin.pro
+++ b/src/proto/popupwin.pro
@@ -5,6 +5,7 @@
void f_popup_clear(typval_T *argvars, typval_T *rettv);
void f_popup_create(typval_T *argvars, typval_T *rettv);
void f_popup_atcursor(typval_T *argvars, typval_T *rettv);
+void f_popup_notification(typval_T *argvars, typval_T *rettv);
int popup_any_visible(void);
void f_popup_close(typval_T *argvars, typval_T *rettv);
void f_popup_hide(typval_T *argvars, typval_T *rettv);