Update doctrine.rst

I updated `.env` and add postgresql configuration

Author: abdounikarim

doctrine.rst

@@ -44,10 +44,13 @@ The database connection information is stored as an environment variable called
     # .env (or override DATABASE_URL in .env.local to avoid committing your changes)
 
     # customize this line!
-    DATABASE_URL="mysql://db_user:db_password@127.0.0.1:3306/db_name"
+    DATABASE_URL="mysql://db_user:db_password@127.0.0.1:3306/db_name?serverVersion=5.7"
 
     # to use sqlite:
     # DATABASE_URL="sqlite:///%kernel.project_dir%/var/app.db"
+    
+    # to use postgresql:
+    # DATABASE_URL="postgresql://db_user:db_password@127.0.0.1:5432/db_name?serverVersion=11&charset=utf8"
 
 .. caution::