LibWeb: Add missing inline-grid for display CSS property

Userland/Libraries/LibWeb/CSS/Identifiers.json

@@ -142,6 +142,7 @@
   "inline",
   "inline-block",
   "inline-flex",
+  "inline-grid",
   "inline-table",
   "inset",
   "inside",

Userland/Libraries/LibWeb/CSS/Properties.json

@@ -609,6 +609,7 @@
       "inline",
       "inline-block",
       "inline-flex",
+      "inline-grid",
       "inline-table",
       "list-item",
       "none",