added .env.example

.env.example

@@ -0,0 +1,8 @@
+# Kalshi environment: demo or prod
+export KALSHI_ENV="demo"
+
+# Your API Key ID (UUID shown when you create the key)
+export KALSHI_API_KEY_ID="REPLACE_ME"
+
+# Path to the downloaded private key (.key) from Kalshi
+export KALSHI_PRIVATE_KEY_PATH="/absolute/path/to/kalshi-private.key"