[TASK] Add " around ignore in .stylelintrc

.stylelintrc is a json-like config and needs
to quote keys.

Releases: master
Resolves: #95785
Change-Id: I626e956af5ffa70f664764fd746c102c73e740be
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71980


Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>

.stylelintrc

@@ -156,7 +156,7 @@
     "selector-type-no-unknown": [
         true,
         {
-            ignore: [
+            "ignore": [
                 "custom-elements"
             ]
         }