env var description

.env.example

@@ -1,9 +1,15 @@
+# rpc for quering shard balances
 REACT_APP_RPC_URL_SHARD0=https://a.api.s0.t.hmny.io/
 REACT_APP_RPC_URL_SHARD1=https://api.s1.t.hmny.io/
 REACT_APP_RPC_URL_SHARD2=https://api.s2.t.hmny.io/
 REACT_APP_RPC_URL_SHARD3=https://api.s3.t.hmny.io/
+# supported shards, comma separated 0,1,2,3
 REACT_APP_AVAILABLE_SHARDS=0,1,2,3
+# explorer v1 api for contract verification. (will migrate to v1 in the future)
 REACT_APP_EXPLORER_V1_API_URL=https://explorer.pops.one:8888/
+# IPFS gateway for tokens assets
 REACT_APP_INDEXER_IPFS_GATEWAY=https://ipfs.io/ipfs/
+# backend websocket API url
 REACT_APP_PROD_ADDRESS=https://explorer-v2-api.hmny.io/
+# dev url
 REACT_APP_DEV_ADDRESS=https://ws.explorer-v2.hmny.io/