Issue templates: add configuration file

This configuration file:
* Continues to allow blank issues to be opened.
* Adds an extra item to the issue template chooser pointing people with support questions to Discussions.

Ref: https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/configuring-issue-templates-for-your-repository#configuring-the-template-chooser

Author: jrfnl

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,5 @@
+blank_issues_enabled: true
+contact_links:
+  - name: Community Support
+    url: https://github.com/PHPCSStandards/PHP_CodeSniffer/discussions?discussions_q=-category%3AAnnouncements
+    about: Support questions belong in Discussions, not in the issue tracker.