Add environment variable for node moniker (#11)

Part of [laconicd testnet validator enrollment](https://www.notion.so/laconicd-testnet-validator-enrollment-6fc1d3cafcc64fef8c5ed3affa27c675)

Co-authored-by: Adw8 <adwaitgharpure@gmail.com>
Reviewed-on: cerc-io/fixturenet-laconicd-stack#11

stack-orchestrator/compose/docker-compose-fixturenet-laconicd.yml

@@ -13,6 +13,7 @@ services:
       AUTHORITY_AUCTION_REVEALS_DURATION: ${AUTHORITY_AUCTION_REVEALS_DURATION}
       AUTHORITY_GRACE_PERIOD: ${AUTHORITY_GRACE_PERIOD}
       GENESIS_FILE: /var/tmp/genesis.json
+      MONIKER: ${MONIKER:-"localtestnet"}
     volumes:
       - laconicd-data:/root/.laconicd
       - genesis-config:/var/tmp

stack-orchestrator/stacks/fixturenet-laconicd/README.md

@@ -113,6 +113,9 @@ Instructions for running a laconicd fixturenet along with registry CLI and conso
 
   # Authority grace period (set bond to authority within this) (in secs) (default: 2 * 24hrs)
   AUTHORITY_GRACE_PERIOD=7200
+
+  # Node moniker (default: "localtestnet")
+  MONIKER=
   ```
 
 * Inside the `laconic-console-deployment` deployment directory, open `config.env` file and set following env variables: