runtime(vim): Update base-syntax, match continued strings and tail comments

Continued strings are currently only matched after operators, in
parenthesised expressions and in function call argument lists.

closes: #14975

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/syntax/testdir/input/vim9_comment.vim b/runtime/syntax/testdir/input/vim9_comment.vim
index fd6a5d2..7d22f46 100644
--- a/runtime/syntax/testdir/input/vim9_comment.vim
+++ b/runtime/syntax/testdir/input/vim9_comment.vim
@@ -34,6 +34,10 @@
   \ continuing comment
   \ continuing comment
 
+var foo = 42 # commment
+  \ continuing comment
+  \ continuing comment
+
 # :Foo
       \ arg1
       #\ comment