Update config.yml

Author: stephencelis

.github/ISSUE_TEMPLATE/config.yml

@@ -11,5 +11,5 @@ contact_links:
     url: https://www.pointfree.co/collections/composable-architecture
     about: Watch videos to get a behind-the-scenes look at how the Composable Architecture was motivated and built
   - name: Slack
-    url: http://pointfree.co/slack-invite
+    url: https://www.pointfree.co/slack-invite
     about: Community chat