feat: finalize file structure for Docker

docker/env.example

@@ -0,0 +1,17 @@
+# Password for the database superuser
+DB_PASSWORD=...
+
+# Legacyworlds database - Main user
+LW_DB_USER_PASS=...
+# Legacyworlds database - Admin user
+LW_DB_ADMIN_PASS=...
+
+# First admin account - User name
+LW_ADMIN_NAME=...
+# First admin account - Email address
+LW_ADMIN_MAIL=...
+# First admin account - Password (warning: will be stored in the clear)
+LW_ADMIN_PASSWORD=...
+
+# "Peacekeepers" fake player - Password (should be a random string)
+LW_PEACEKEEPERS_PASSWORD=...