docs(readme): add configuration step for env and docker files

- add instructions to rename .env.example files
- add docker-compose.override.yml setup step

README.md

@@ -15,6 +15,14 @@ A simple QR code generator.
 -   Make (optional, but recommended)
 -   Linux (tested environment)
 
+## Configuration
+
+Before installation, rename the example files:
+
+- `./app/.env.example` → `./app/.env`
+- `./app/internal/view/front/.env.example` → `./app/internal/view/front/.env`
+- `./docker-compose.override.yml.example` → `./docker-compose.override.yml`
+
 ## Installation
 
 ``` bash