refactor(crawlerConfig): nest selectors under default key for better organization

Author: zhensherlock

crawlerConfig.json

@@ -4,20 +4,22 @@
   "rateLimit": 8,
   "maxDepth": 10,
   "selectors": {
-    "lvl0": {
-      "selector": "",
-      "defaultValue": "Documentation"
-    },
-    "lvl1": ".content h1",
-    "lvl2": ".content h2",
-    "lvl3": ".content h3",
-    "lvl4": ".content h4",
-    "lvl5": ".content h5",
-    "content": ".content p, .content li",
-    "lang": {
-      "selector": "/html/@lang",
-      "type": "xpath",
-      "global": true
+    "default": {
+      "lvl0": {
+        "selector": "",
+        "default_value": "Documentation"
+      },
+      "lvl1": ".content h1",
+      "lvl2": ".content h2",
+      "lvl3": ".content h3",
+      "lvl4": ".content h4",
+      "lvl5": ".content h5",
+      "content": ".content p, .content li",
+      "lang": {
+        "selector": "/html/@lang",
+        "type": "xpath",
+        "global": true
+      }
     }
   },
   "selectors_exclude": [