Added missing itemsPerPage param for short URLs endpoint to swagger docs

docs/swagger/paths/v1_short-urls.json

@@ -19,6 +19,15 @@
                     "type": "integer"
                 }
             },
+            {
+                "name": "itemsPerPage",
+                "in": "query",
+                "description": "The amount of items to return on every page. Defaults to 10",
+                "required": false,
+                "schema": {
+                    "type": "number"
+                }
+            },
             {
                 "name": "searchTerm",
                 "in": "query",