opl: added quickstart & monitoring link

docs/dapp/opl/README.md

@@ -11,13 +11,71 @@ The Oasis Privacy Layer contains a set of [smart contracts](https://github.com/o
 that integrate [Sapphire](../sapphire/README.mdx) into your existing and future
 Web3 applications, introducing confidentiality.
 
-Application developers on any EVM-compatible network can add confidential state
-and selective disclosures to their application through the usage of a smart
-contract deployed on OPL without migrating their application stack. OPL enabled
-smart contracts provide a default bridge for developers to pass messages
-between Sapphire and other networks.
+Application developers on any supported network can add confidential state
+and selective disclosures to their applications through the usage of a smart
+contract deployed on OPL without leaving their existing networks.
 
 For more information about OPL and to catch the latest news, please visit the
 official [page](https://oasisprotocol.org/opl).
 
 ![Oasis Privacy Layer diagram](../images/opl/privacy-layer-diagram.png)
+
+## Supported Networks
+
+### Mainnets
+
+ * Ethereum (1), BNB Chain (56), Polygon (137), Fantom (250), Avalanche (43114), Arbitrum One (42161), Moonriver (1285), Optimism (10), Aurora (1313161554), Syscoin (57), Astar (592), Ape (16350), Arbitrum Nova (42170), Milkomeda C1 (2001), zkSync Era (324), Filecoin (314), Polygon zkEVM (1101), Oasis Sapphire (23294)
+
+### Testnets
+
+ * Goerli Testnet (5), BSC Testnet (97), Fantom Testnet (4002), Arbitrum Testnet (421611), Polygon Mumbai Testnet (80001), Avalanche C-Chain Fuji Testnet (43113), Dexalot Testnet (432201), Godwoken Testnet (71401), Shibuya Testnet (81), ConsenSys zkEVM Testnet (59140), Filecoin Hyperspace Testnet (3141), Polygon zkEVM Testnet (1442), Scroll Alpha Testnet (534353), FNCY Testnet (923018)
+
+
+## Quickstart
+
+A pair of contracts are linked bidirectionally to each other across chains, with one end on Sapphire and the other on a supported EVM compatible chain (the Home Network). They can post and receive messages to & from each other using the message-passing bridge, but must register endpoints to define which messages they handle.
+
+Start by adding the [`sapphire-contracts`](http://npmjs.com/package/@oasisprotocol/sapphire-contracts) package to your project so you can import `OPL.sol`:
+
+    pnpm add @oasisprotocol/sapphire-contracts
+
+Then define the two contracts, starting with a contract on Sapphire which runs inside the confidential enclave and can be called via the `secretExample` handler. Use the constructor to provide the Sapphire contract with the location (address and chain) of the contract on the other network::
+
+```solidity
+import {Enclave, Result, autoswitch} from "@oasisprotocol/sapphire-contracts/contracts/OPL.sol";
+
+contract SapphireContract is Enclave {
+    constructor(address otherEnd, string chain) Enclave(otherEnd, autoswitch(chain)) {
+        registerEndpoint("secretExample", on_example);
+    }
+    function on_example(bytes calldata _args) internal returns (Result) {
+        (uint256 a, bool b) = abi.decode(args, (uint256, bool));
+        // TODO: do confidential things here
+        return Result.Success;
+    }
+}
+```
+
+Then on the other chain, define your contract which can be called via `triggerExample` to send a message to the contract on Sapphire using the `postMessage` interface.
+
+```solidity
+import {Host, Result} from "@oasisprotocol/sapphire-contracts/contracts/OPL.sol";
+
+contract HomeContract is Host {
+    constructor(address otherEnd) Host(otherEnd) {
+    }
+    function triggerExample (uint256 a, bool b) external payable {
+        postMessage("secretExample", abi.encode(a, b));
+    }
+}
+```
+
+After a few minutes the bridge will detect and then execute the `SapphireContract.on_example` method.
+
+## Monitoring
+
+The Celer IM Scan API can be used to retrieve status and message details by providing the globally unique transaction ID from the chain which originated the message.
+
+    https://api.celerscan.com/scan/searchByTxHash?tx=0x...
+
+For details of the response format, see the [Query IM Tx Status](https://im-docs.celer.network/developer/development-guide/query-im-tx-status) page of the Celer Inter-Chain Message (IM) documentation.