use ENV variables instead of hardcoded values

docker/envrionment.env

@@ -0,0 +1,10 @@
+MYSQL_ROOT_PASSWORD=root 
+MYSQL_DATABASE=wordpress 
+MYSQL_USER=wp_admin
+MYSQL_PASSWORD=wp_password
+
+API_URL=http://localhost:8081
+
+REACT_APP_TEST_URL=http://localhost:8000/api-wiaas
+REACT_APP_PROD_URL=http://localhost:8000/api-wiaas
+REACT_APP_DEV_URL=${API_URL}