some changes for docker setup (#9)

* added SIGTERM handler for graceful docker shutdown

* added error message

* added example for bitcoind running on the host undockered

* added docker-compose and extended example

* added docker-compose section to README

* addes some note for rpcallowip

* added restart policy

* added DB folder for persistent data

* added $NETWORK as prefix for database path to not get in conflict with testnet setup

* used env variables for stratum and api ports

docker-compose.yml

@@ -0,0 +1,20 @@
+version: '3.8'
+
+services:
+  public-pool:
+    container_name: public-pool
+    build:
+      context: .
+      dockerfile: Dockerfile
+    restart: unless-stopped
+    extra_hosts:
+      - "host.docker.internal:host-gateway"
+    ports:
+      - "127.0.0.1:${STRATUM_PORT}:${STRATUM_PORT}/tcp"
+      - "127.0.0.1:${API_PORT}:${API_PORT}/tcp"
+    volumes:
+      - "./${NETWORK}-DB:/public-pool/DB"
+      - "./.env:/public-pool/.env:ro"
+    environment:
+      - NODE_ENV=production
+