Update 'README.md'

README.md

@@ -1,3 +1,10 @@
 # esp32_ota_example
-## simple example for using esp_ota_updater to update esp32 or esp8266 from gita or gitea
-### 
+simple example for using esp_ota_updater to update esp32 or esp8266 from gita or gitea
+## project structure
+```
+ main.py
+ boot.py
+ app/---
+    start.py
+    ...
+```