Add forum link to the issue choose page

Signed-off-by: Álvaro Brey <alvaro.brey@nextcloud.com>

.github/ISSUE_TEMPLATE/config.yml

@@ -1 +1,5 @@
-blank_issues_enabled: false
+blank_issues_enabled: false
+contact_links:
+    -   name: Community Support and Help
+        url: https://help.nextcloud.com/
+        about: For questions and general help