add a json reporter

src/keyword_spotting/reporter.py

@@ -0,0 +1,19 @@
+import os
+import json
+
+class Reporter:
+    def __init__(self, experiment_path, filename):
+        self.experiment_path = experiment_path
+        self.file_name = filename
+        self.output_file = os.path.join(experiment_path, self.file_name)
+        self.data = {}
+
+    def __del__(self): 
+        with open(self.output_file , 'w', encoding='utf-8') as f:
+            json.dump(self.data, f, ensure_ascii=False, indent=4)
+
+    def report(self, key, data):
+        self.data[key] = data
+
+    def load(self, filepath):
+        self.data = json.load(open(filepath, 'r'))