housekeeping: Add a configuration file for issues

Author: glennawatson

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,9 @@
+blank_issues_enabled: false
+contact_links:
+  - name: Questions
+    url: https://github.com/reactiveui/ReactiveUI/discussions
+    about: 'For general questions about ReactiveUI, ask in the GitHub discussions'
+chat:
+  - name: Chat
+    url: https://www.reactiveui.net/slack
+    about: 'Our slack chat community invite'