[3.7] bpo-35054: Add more index entries for symbols. (GH-10064). (GH-10120)

(cherry picked from commit ddb961d2abe5d5fde76d85b21a77e4e91e0043ad)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Doc/tutorial/introduction.rst b/Doc/tutorial/introduction.rst
index e68c9b1..f5a394a 100644
--- a/Doc/tutorial/introduction.rst
+++ b/Doc/tutorial/introduction.rst
@@ -11,6 +11,8 @@
 line by itself in an example means you must type a blank line; this is used to
 end a multi-line command.
 
+.. index:: single: #; comment
+
 Many of the examples in this manual, even those entered at the interactive
 prompt, include comments.  Comments in Python start with the hash character,
 ``#``, and extend to the end of the physical line.  A comment may appear at the