Updated postgres version in app.json: 13.5 > 13

Author: LuigiImVector

README.md

@@ -40,6 +40,8 @@ Un-official Telegram bot of [free-programming-books](https://github.com/EbookFou
 
 7. Open `https://app-name.herokuapp.com/` if the bot doesn't start (mainly the first time)
 
+If you want to test the app locally before committing, read [Heroku documentation](https://devcenter.heroku.com/articles/heroku-local).
+
 
 #### Improve code
 

app.json

@@ -21,7 +21,7 @@
         {
           "plan": "heroku-postgresql:hobby-dev",
           "options": {
-            "version": "13.5"
+            "version": "13"
           }
         }
     ],