Add example environment configuration and Docker Compose setup

- Introduced a new `.env.example` file to provide a template for environment variables used by the Scratchbox server.
- Added a `docker-compose.example.yml` file to facilitate easy deployment of the Scratchbox service with Docker.
- Updated `docker-entrypoint.sh` to enforce environment variable settings for server configuration.
- Removed the generation of a config key file from the workflow, simplifying the configuration process.
- Adjusted the README.md to reflect changes in configuration management and usage instructions.

.env.example

@@ -0,0 +1,39 @@
+# Scratchbox env-mode example for `scratchbox server --env`.
+# Set values here and pass this file with `--env-file .env`.
+#
+# IMPORTANT:
+# - Scratchbox stores its key at $SCRATCHBOX_STORAGE_DATA_DIR/metadata.key.
+# - Keep that data directory persistent across restarts.
+
+# server
+SCRATCHBOX_SERVER_READ_HEADER_TIMEOUT=5s
+SCRATCHBOX_SERVER_READ_TIMEOUT=30s
+SCRATCHBOX_SERVER_WRITE_TIMEOUT=30s
+SCRATCHBOX_SERVER_IDLE_TIMEOUT=120s
+SCRATCHBOX_SERVER_MAX_HEADER_BYTES=1048576
+SCRATCHBOX_SERVER_ACCESS_LOG_ENABLED=true
+
+# limits
+SCRATCHBOX_LIMITS_MAX_UPLOAD_SIZE=100MiB
+SCRATCHBOX_LIMITS_DEFAULT_TTL=15m
+SCRATCHBOX_LIMITS_RAW_CACHE_MAX_SIZE=200MiB
+SCRATCHBOX_LIMITS_RAW_CACHE_MAX_ENTRIES=32
+
+# storage
+SCRATCHBOX_STORAGE_CLEANUP_INTERVAL=1m
+
+# security
+# Comma-separated IP/CIDR list. Empty = unrestricted.
+SCRATCHBOX_SECURITY_ALLOWED_IPS=127.0.0.1 # This should be set to your networks CIDR like 192.168.2.0/24 or a particulat IP like 192.168.2.55.
+SCRATCHBOX_SECURITY_TRUST_PROXY_HEADERS=false
+# Comma-separated IP/CIDR list.
+SCRATCHBOX_SECURITY_TRUSTED_PROXY_IPS= # Same as SCRATCHBOX_SECURITY_ALLOWED_IPS just Trusted Proxies you expect clients to come from instead.
+SCRATCHBOX_SECURITY_RATE_LIMIT_UI_ENABLED=false
+SCRATCHBOX_SECURITY_RATE_LIMIT_UI_REQUESTS_PER_MINUTE=360
+SCRATCHBOX_SECURITY_RATE_LIMIT_UI_BURST=120
+SCRATCHBOX_SECURITY_RATE_LIMIT_API_READ_ENABLED=false
+SCRATCHBOX_SECURITY_RATE_LIMIT_API_READ_REQUESTS_PER_MINUTE=300
+SCRATCHBOX_SECURITY_RATE_LIMIT_API_READ_BURST=100
+SCRATCHBOX_SECURITY_RATE_LIMIT_API_WRITE_ENABLED=true
+SCRATCHBOX_SECURITY_RATE_LIMIT_API_WRITE_REQUESTS_PER_MINUTE=30
+SCRATCHBOX_SECURITY_RATE_LIMIT_API_WRITE_BURST=10