patch 9.1.0936: cannot highlight completed text

Problem:  cannot highlight completed text
Solution: (optionally) highlight auto-completed text using the
          ComplMatchIns highlight group (glepnir)

closes: #16173

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/fold.txt b/runtime/doc/fold.txt
index 61f3b67..cf92089 100644
--- a/runtime/doc/fold.txt
+++ b/runtime/doc/fold.txt
@@ -160,7 +160,7 @@
 fold levels on previous lines until an independent fold level is found.
 
 If this proves difficult, the next best thing could be to cache all fold levels
-in a buffer-local variable (b:foldlevels) that is only updated on |b:changedtick|: 
+in a buffer-local variable (b:foldlevels) that is only updated on |b:changedtick|:
 >vim
   vim9script
   def MyFoldFunc(): number
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index eb6c3b2..7640ee1 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -1,4 +1,4 @@
-*syntax.txt*	For Vim version 9.1.  Last change: 2024 Dec 12
+*syntax.txt*	For Vim version 9.1.  Last change: 2024 Dec 16
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -5857,6 +5857,8 @@
 PmenuMatch	Popup menu: Matched text in normal item.
 							*hl-PmenuMatchSel*
 PmenuMatchSel	Popup menu: Matched text in selected item.
+							*hl-ComplMatchIns*
+ComplMatchIns	Matched text of the currently inserted completion.
 							*hl-PopupNotification*
 PopupNotification
 		Popup window created with |popup_notification()|.  If not
diff --git a/runtime/doc/tags b/runtime/doc/tags
index a8b4987..56004e9 100644
--- a/runtime/doc/tags
+++ b/runtime/doc/tags
@@ -8136,6 +8136,7 @@
 hitest.vim	syntax.txt	/*hitest.vim*
 hjkl	usr_02.txt	/*hjkl*
 hl-ColorColumn	syntax.txt	/*hl-ColorColumn*
+hl-ComplMatchIns	syntax.txt	/*hl-ComplMatchIns*
 hl-Conceal	syntax.txt	/*hl-Conceal*
 hl-CurSearch	syntax.txt	/*hl-CurSearch*
 hl-Cursor	syntax.txt	/*hl-Cursor*
diff --git a/runtime/doc/todo.txt b/runtime/doc/todo.txt
index b1318cf..342332e 100644
--- a/runtime/doc/todo.txt
+++ b/runtime/doc/todo.txt
@@ -1,4 +1,4 @@
-*todo.txt*      For Vim version 9.1.  Last change: 2024 Dec 04
+*todo.txt*      For Vim version 9.1.  Last change: 2024 Dec 16
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -1093,9 +1093,6 @@
 MS-Windows: buffer completion doesn't work when using backslash (or slash)
 for a path separator. (xtal8, #2201)
 
-Would be nice for Insert mode completion to highlight the text that was added
-(and may change when picking another completion).
-
 Test more runtime files.
 
 Window not closed when deleting buffer. (Harm te Hennepe, 2017 Aug 27, #2029)
diff --git a/runtime/doc/version9.txt b/runtime/doc/version9.txt
index bcda3d0..8993e3c 100644
--- a/runtime/doc/version9.txt
+++ b/runtime/doc/version9.txt
@@ -41653,6 +41653,7 @@
 
 Highlighting: ~
 
+|hl-ComplMatchIns|	matched text of the currently inserted completion.
 |hl-MsgArea|		highlighting of the Command-line and messages area
 |hl-PmenuMatch|		Popup menu: highlighting of matched text
 |hl-PmenuMatchSel|	Popup menu: highlighting of matched text in selected