docs: add Stack Overflow & Discussions templates

Author: ghiscoding

.github/ISSUE_TEMPLATE/config.yml

@@ -1,5 +1,8 @@
 blank_issues_enabled: false
 contact_links:
-  - name: Questions & Discussions
+  - name: Questions
+    url: https://stackoverflow.com/search?q=slickgrid
+    about: Use Stack Overflow to find or ask for any related SlickGrid questions
+  - name: Discussions
     url: https://github.com/ghiscoding/Angular-Slickgrid/discussions
     about: Use GitHub discussions for message-board style questions and discussions.