Makefile: inform rstcheck about the new card directive

Makefile

@@ -13,7 +13,7 @@ venv:
 check: venv
 	# ignore-messages is needed due to links being used in directives, which
 	# are not visible by rstcheck as these directives are ignored (mostly faq)
-	venv/bin/rstcheck --recursive --ignore-directives tabs,faq,product-table \
+	venv/bin/rstcheck --recursive --ignore-directives card,tabs,faq,product-table \
 		--ignore-messages "faq(.*)Hyperlink target(.*)is not referenced" \
 		source