ISSUE_TEMPLATE: for bugs, ask questions on the mailing list

and try to add the top comment within an HTML comment in the hope
that it might get hidden if the text is kept

.github/ISSUE_TEMPLATE

@@ -1,5 +1,9 @@
-[ There are collections of known issues to be aware of:
-  https://curl.haxx.se/docs/knownbugs.html https://curl.haxx.se/docs/todo.html ]
+<!-- Only file bugs here! Questions should be taken on the mailing list,
+     see https://curl.haxx.se/mail/
+
+     There are collections of known issues to be aware of:
+     https://curl.haxx.se/docs/knownbugs.html
+     https://curl.haxx.se/docs/todo.html       -->
 
 ### I did this
 
@@ -7,6 +11,6 @@
 
 ### curl/libcurl version
 
-[curl -V output perhaps?]
+[curl -V output]
 
 ### operating system