chore: Link to discussions and Discord in new issues

Author: dbanty

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,8 @@
+blank_issues_enabled: false
+contact_links:
+  - name: GitHub Discussions
+    url: https://github.com/openapi-generators/openapi-python-client/discussions
+    about: Please ask and answer questions here.
+  - name: Discord
+    url: https://discord.gg/JaqVvBgwYw
+    about: Less structured, more casual chat.