add get custom metadata field method

Author: bishosilwal

lib/imagekitio/client.rb

@@ -149,7 +149,11 @@ def bulk_job_status(job_id)
     end
 
     def create_custom_metadata_fields(name, label, schema)
-      @file.create_custom_metadata_fields(name, label, schema)
+      @file.create_custom_metadata(name, label, schema)
+    end
+
+    def get_custom_metadata(options = {})
+      @file.get_custom_metadata(options)
     end
 
     def phash_distance(first, second)

lib/imagekitio/file.rb

@@ -226,6 +226,12 @@ def create_custom_metadata(name, label, schema)
       @req_obj.request('post', url, @req_obj.create_headers, payload)
     end
 
+    def get_custom_metadata(options)
+      url = "#{constants.API_BASE_URL}/customMetadataFields"
+      payload = request_formatter(options)
+      @req_obj.request('get', url, @req_obj.create_headers, payload)
+    end
+
     def validate_upload_options(options)
 
       #  Validates upload value, checks if params are valid,