Add .env.sample and link it in docker-compose for env management

Author: malkoG

.env.sample

@@ -0,0 +1 @@
+OPENAI_API_KEY=sk-proj-xxxxx

docker-compose.yml

@@ -15,6 +15,8 @@ services:
       - ./pythonkr_backend:/app/pythonkr_backend
     ports:
       - "8080:8080"
+    env_file:
+      - .env
     depends_on:
       - db
     environment:
@@ -23,4 +25,4 @@ services:
       POSTGRES_PASSWORD: pktesting
 
 volumes:
-  postgres_data:
+  postgres_data: