docs: add instruction on customisation

Author: realnimish

packages/contracts/.env.example

@@ -1,3 +1,4 @@
+NETWORK=sepolia
 REMOTE_GATEWAY=
 DEPLOYER_KEY=
 SIGNER_ADDR=

packages/gateway/README.md

@@ -6,12 +6,12 @@ You can run the gateway as a command line tool; in its default configuration it
 
 ```
 yarn && yarn build
-yarn start --private-key 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80 --data test.eth.json
+yarn start --private-key 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80 --provider-url <url>
 ```
 
 `private-key` should be an Ethereum private key that will be used to sign messages. You should configure your resolver contract to expect messages to be signed using the corresponding address.
 
-`data` is the path to the data file; an example file is provided in `test.eth.json`.
+`<url>` is the websocket endpoint of the target substrate chain (default: wss://ws.test.azero.dev)
 
 ## Customisation
 The JSON backend is implemented in [json.ts](src/json.ts), and implements the `Database` interface from [server.ts](src/server.ts). You can replace this with your own database service by implementing the methods provided in that interface. If a record does not exist, you should return the zero value for that type - for example, requests for nonexistent text records should be responded to with the empty string, and requests for nonexistent addresses should be responded to with the all-zero address.
@@ -25,3 +25,6 @@ const db = JSONDatabase.fromFilename(options.data, parseInt(options.ttl));
 const app = makeApp(signer, '/', db);
 app.listen(parseInt(options.port));
 ```
+
+## AZERO-ID implementation
+The AzeroId gateway implementation in [azero-id.ts](src/azero-id.ts) reads the state from the AZERO-ID registry contract on AlephZero network. [supported-tlds.json](src/supported-tlds.json) stores the TLDs mapped to their target registry. Update it as per need.