patch 9.1.0312: heredocs are not supported for :commands

Problem:  heredocs are not supported for :commands
          (@balki)
Solution: Add heredoc support
          (Yegappan Lakshmanan)

fixes: #14491
closes: #14528

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/vim9.txt b/runtime/doc/vim9.txt
index 7dd2ab0..ffb5c2e 100644
--- a/runtime/doc/vim9.txt
+++ b/runtime/doc/vim9.txt
@@ -1,4 +1,4 @@
-*vim9.txt*	For Vim version 9.1.  Last change: 2024 Jan 12
+*vim9.txt*	For Vim version 9.1.  Last change: 2024 Apr 12
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -641,6 +641,14 @@
 The block can also be used for defining a user command.  Inside the block Vim9
 syntax will be used.
 
+This is an example of using here-docs: >
+    com SomeCommand {
+        g:someVar =<< trim eval END
+          ccc
+          ddd
+        END
+      }
+
 If the statements include a dictionary, its closing bracket must not be
 written at the start of a line.  Otherwise, it would be parsed as the end of
 the block.  This does not work: >