docs: add issue templates (bug report, feature request)

GitHub issue forms that enforce the fields needed to triage: obscura
version, OS and architecture, how it is being used, stealth mode, a
reproduction, expected vs actual, and whether headless Chrome behaves
the same. config.yml routes questions and API proposals to Discussions
and security reports to the private advisory flow.

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,8 @@
+blank_issues_enabled: false
+contact_links:
+  - name: Questions and API proposals
+    url: https://github.com/h4ckf0r0day/obscura/discussions
+    about: Ask questions or propose larger API designs in Discussions.
+  - name: Report a security vulnerability
+    url: https://github.com/h4ckf0r0day/obscura/security/advisories/new
+    about: Report security issues privately, not as a public issue. See SECURITY.md.