Env. vars: set default values and related docs

README.md

@@ -74,9 +74,31 @@ services:
     tty: true
     image: wayback_machine_downloader:latest
     container_name: wayback_machine_downloader
+    environment:
+      - ENVIRONMENT=${ENVIRONMENT:-development}
+      - OPTIONS=${OPTIONS:-""}
+      - TARGET_URL=${TARGET_URL}
     volumes:
       - .:/build:rw
       - ./websites:/build/websites:rw
+    command: --directory /build/websites ${OPTIONS} ${TARGET_URL}
+```
+#### Usage:
+Now You can create a Docker image as named "wayback_machine_downloader" with the following command:
+```bash
+docker compose up -d --build
+```
+
+After that you must set TARGET_URL environment variable:
+```bash
+export TARGET_URL="https://example.com/"
+```
+
+The **OPTIONS** env. variable is optional this may include additional settings which are found in the "**Advanced usage**" section below.
+
+Example:
+```bash
+export OPTIONS="--list -f 20060121"
 ```
 
 ## ⚙️ Configuration

docker-compose.yml

@@ -6,7 +6,9 @@ services:
     image: wayback_machine_downloader:latest
     container_name: wayback_machine_downloader
     environment:
-      - ENVIRONMENT=${ENVIRONMENT}
+      - DEVELOPMENT=${DEVELOPMENT:-production}
+      - OPTIONS=${OPTIONS:-""}
+      - TARGET_URL=${TARGET_URL}
     volumes:
       - .:/build:rw
       - ./websites:/build/websites:rw