Add Docker support

Dockerfile

@@ -0,0 +1,5 @@
+FROM romeoz/docker-apache-php:7.3
+
+COPY . /app
+
+RUN cp /app/announce.php /var/www/app/

announce.php

@@ -66,7 +66,7 @@ define('__NO_SEED_P2P', true);
  * On Linux, you should use /dev/shm as it is very fast.
  * On Windows, you will need to change this value to some other valid path such as C:/Peers.txt
  */
-define('__LOCATION_PEERS', 'peers.txt');
+define('__LOCATION_PEERS', '/var/www/app/data/peers.txt');
 
 /**
  * Should we enable short announces?

docker-compose.yml

@@ -0,0 +1,8 @@
+version: "3.5"
+services:
+  tracker:
+    build: .
+    ports:
+      - 8081:80
+    volumes:
+      - tracker-peers-data:/var/www/app/data/