FEATURE: Ignore custom element selectors in stylelint

This change is due to the usage of custom web components, as used in
Translucent.

configs/stylelintrc.yml

@@ -6,5 +6,11 @@
 extends: stylelint-config-standard
 
 rules:
-    indentation: 4
-    declaration-colon-space-before: null
+
+  indentation: 4
+
+  declaration-colon-space-before: null
+
+  selector-type-no-unknown:
+    ignore:
+      - custom-elements