added env variables for ethscan crawler

crawlers/sample.env

@@ -2,3 +2,7 @@
 export MOONSTREAM_IPC_PATH=null
 export MOONSTREAM_CRAWL_WORKERS=4
 export MOONSTREAM_DB_URI="postgresql://<username>:<password>@<db_host>:<db_port>/<db_name>"
+
+export ETH_SCAN_TOKEN="TOKEN"
+export AWS_S3_SMARTCONTRACT_BUCKET=""
+export AWS_S3_SMARTCONTRACT_BUCKET_CONTRACT_PREFIX=""