Fix exporter schema to support multiple entries per file. (#15649)

integrations/schemas/exporter.json

@@ -1,7 +1,20 @@
 {
   "$schema": "http://json-schema.org/draft-07/schema#",
-  "type": "object",
   "title": "Netdata Agent data exporter metadata.",
+  "oneOf": [
+    {
+      "$ref": "#/$defs/entry"
+    },
+    {
+      "type": "array",
+      "minLength": 1,
+      "items": {
+        "$ref": "#/$defs/entry"
+      }
+    }
+  ],
+  "$defs": {
+    "entry": {
       "properties": {
         "id": {
           "$ref": "./shared.json#/$defs/id"
@@ -42,3 +55,5 @@
         "setup"
       ]
     }
+  }
+}