runtime(doc): add help tag multiple-constructors. (#13772)

Signed-off-by: Ernie Rael <errael@raelity.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

Author: errael

runtime/doc/tags

@@ -8686,6 +8686,7 @@ multilang	mlang.txt	/*multilang*
 multilang-menus	mlang.txt	/*multilang-menus*
 multilang-messages	mlang.txt	/*multilang-messages*
 multilang-scripts	mlang.txt	/*multilang-scripts*
+multiple-constructors	vim9class.txt	/*multiple-constructors*
 myfiletypefile	syntax.txt	/*myfiletypefile*
 myscriptsfile	syntax.txt	/*myscriptsfile*
 mysql	ft_sql.txt	/*mysql*

runtime/doc/vim9class.txt

@@ -1,4 +1,4 @@
-*vim9class.txt*	For Vim version 9.0.  Last change: 2023 Dec 24
+*vim9class.txt*	For Vim version 9.0.  Last change: 2023 Dec 25
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -212,6 +212,8 @@ the above class): >
 <
 Simplifying the new() method ~
 						*new()* *constructor*
+See also |default-constructor| and |multiple-constructors|.
+
 Many constructors take values for the object variables.  Thus you very often
 see this pattern: >
 
@@ -801,7 +803,7 @@ first.
 
 
 Multiple constructors ~
-
+						*multiple-constructors*
 Normally a class has just one new() constructor.  In case you find that the
 constructor is often called with the same arguments you may want to simplify
 your code by putting those arguments into a second constructor method.  For