feat: Add browsingData namespace to metadata

The auto-generated output from the metadata generator also includes the
following methods from Chrome. Firefox does not support them, so they
were not included in the metadata:

```
    "removeAppcache": {
      "minArgs": 1,
      "maxArgs": 1
    },
    "removeFileSystems": {
      "minArgs": 1,
      "maxArgs": 1
    },
    "removeIndexedDB": {
      "minArgs": 1,
      "maxArgs": 1
    },
    "removeWebSQL": {
      "minArgs": 1,
      "maxArgs": 1
    },
```

Also see:
https://searchfox.org/mozilla-central/rev/292d295d6b084b43b70de26a42e68513bb7b36a3/browser/components/extensions/schemas/browsing_data.json
https://developer.mozilla.org/en-US/Add-ons/WebExtensions/API/browsingData#Browser_compatibility

api-metadata.json

@@ -93,6 +93,48 @@
       "maxArgs": 1
     }
   },
+  "browsingData": {
+    "remove": {
+      "minArgs": 2,
+      "maxArgs": 2
+    },
+    "removeCache": {
+      "minArgs": 1,
+      "maxArgs": 1
+    },
+    "removeCookies": {
+      "minArgs": 1,
+      "maxArgs": 1
+    },
+    "removeDownloads": {
+      "minArgs": 1,
+      "maxArgs": 1
+    },
+    "removeFormData": {
+      "minArgs": 1,
+      "maxArgs": 1
+    },
+    "removeHistory": {
+      "minArgs": 1,
+      "maxArgs": 1
+    },
+    "removeLocalStorage": {
+      "minArgs": 1,
+      "maxArgs": 1
+    },
+    "removePasswords": {
+      "minArgs": 1,
+      "maxArgs": 1
+    },
+    "removePluginData": {
+      "minArgs": 1,
+      "maxArgs": 1
+    },
+    "settings": {
+      "minArgs": 0,
+      "maxArgs": 0
+    }
+  },
   "commands": {
     "getAll": {
       "minArgs": 0,