Add issue template chooser and mention discourse in bug report template

.github/ISSUE_TEMPLATE/bug_report.md

@@ -7,6 +7,16 @@ assignees: ''
 
 ---
 
+<!--
+If you are a user of OpenMC and are running into trouble with the code or are
+seeking general user support, we highly recommend posting on the OpenMC
+discourse forum first. GitHub issues should be used specifically for bug reports
+and feature requests.
+
+https://openmc.discourse.group/
+
+-->
+
 ## Bug Description
 <!--A clear and concise description of the problem (Note: A missing feature is not a bug).-->
 

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,5 @@
+blank_issues_enabled: true
+contact_links:
+  - name: Troubleshooting and User Support
+    url: https://openmc.discourse.group/
+    about: For user support and troubleshooting, please use our Discourse forum