Add example env

.env.example

@@ -0,0 +1,21 @@
+# Required: BIP39 mnemonic for the merchant XO Engine wallet
+ENGINE_MNEMONIC=<your mnemonic here separated by spaces>
+
+# XO Engine local state
+ENGINE_DATABASE_PATH=./data/xo
+ENGINE_DATABASE_FILENAME=engine.db
+
+# 3rd-party invitation sync server (same protocol as xo-cli)
+SYNC_SERVER_URL=https://sync.xo.harvmaster.com
+
+# Merchant display name on receipts
+MERCHANT_NAME=XO Snack Machine
+
+# Vending catalog/orders database
+DATABASE_PATH=data/data.db
+
+# HTTP server
+SERVER_PORT=3000
+SERVER_HOST=localhost
+
+DEBUG=vending-machine*