Add a "no support" note to issue template

.github/ISSUE_TEMPLATE.md

@@ -1,4 +1,13 @@
-Please supply the following with bug reports to allow for diagnostics:
+Please only open issues for bug reports or feature requests.
+The developers do not have the resources to provide individual support.
+For support, please turn to the most applicable Stack Exchange site, such as
+[Information Security](https://security.stackexchange.com/),
+[Network Engineering](https://networkengineering.stackexchange.com/) or
+[Super User](https://superuser.com/).
+For user discussions, there is an experimental Gitter chat at
+[gitter.im/droe/sslsplit](https://gitter.im/droe/sslsplit).
+
+For bug reports, please supply:
 
 -   Output of `sslsplit -V`
 -   Output of `uname -a`