Add smoke-all test for fr-CA language variant (#14014)

Verifies that lang: fr-CA correctly applies regional overrides (Auteur(-trice)) while inheriting base French translations  (Date de publication).

Author: cderv

tests/docs/smoke-all/2026/02/11/14014.qmd

@@ -0,0 +1,15 @@
+---
+title: "French Canadian language variant"
+lang: fr-CA
+author: Jean Tremblay
+date: 2026-02-11
+format: html
+_quarto:
+  tests:
+    html:
+      ensureFileRegexMatches:
+        - ['Auteur\(-trice\)', 'Date de publication']
+        - ['Auteur·rice']
+---
+
+Content to verify `lang: fr-CA` applies regional French translations, while still using main `lang: fr` translation.