docs(repos-config): add Query Filters library to gravitykit.dev

Adds GravityKit/Query-Filters (develop) as a product so its developer
hooks/API are generated and published to gravitykit.dev. Filed under the
GravityKit Products category. Local generation verified: 22 filter hooks;
no public PHP API symbols exposed (library, non-fullApi).

Once deployed, the daily Algolia DocSearch crawler indexes the new pages
via the per-product sitemap.

Author: zackkatz

repos-config.json

@@ -278,6 +278,13 @@
       "category": "gravitykit",
       "purchaseUrl": "https://www.gravitykit.com/products/gravitysearch/"
     },
+    {
+      "id": "query-filters",
+      "repo": "GravityKit/Query-Filters",
+      "label": "Query Filters",
+      "description": "Advanced filtering for Gravity Forms' GF_Query and form fields — the shared library behind Advanced Filter, GravityExport, GravityCalendar, GravityCharts, and GravityBoard.",
+      "category": "gravitykit"
+    },
     {
       "id": "gravityflow",
       "repo": "gravityforms/gravityflow",