feat(coc#pum#has_item_selected) (#5064)

This commit add a function to check if there is a item selected in
completion list.

Solve #5063.

autoload/coc/pum.vim

@@ -22,6 +22,13 @@ if s:is_vim
   endif
 endif
 
+function! coc#pum#has_item_selected() abort
+    if s:pum_winid == -1
+        return 0
+    endif
+    return s:pum_index != -1
+endfunction
+
 function! coc#pum#visible() abort
   if s:pum_winid == -1
     return 0

doc/coc.txt

@@ -2171,6 +2171,11 @@ coc#pum#visible() 					*coc#pum#visible()*
 	Check if customized popupmenu is visible like |pumvisible()| does.
 	Return 1 when popup menu is visible.
 
+coc#pum#has_item_selected()				*coc#pum#has_item_selected*
+
+	Check if there is a completion item selected in the popup menu.
+	Return 1 when there has been a completion item selected.
+
 coc#pum#next({insert}) 					*coc#pum#next()*
 
 	Select next item of customized popupmenu, insert word when {insert} is