op-node: update readme (#3282)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

op-node/README.md

-# opnode
+# op-node
 
 This is the reference implementation of the [rollup-node spec](../specs/rollup-node.md).
 
 ## Compiling
 
-From the repository root:
+Compile a binary:
+```shell
+cd op-node
+go build -o bin/op-node ./cmd
+```
+
+## Testing
 
+Run op-node unit tests:
 ```shell
-go build -o op ./op-node/cmd
-go test ./op-node/...
+cd op-node
+go test ./...
+```
+
+Run end-to-end tests:
+```shell
+cd op-e2e
+go test ./...
 ```
 
 ## Running
@@ -16,7 +29,7 @@ go test ./op-node/...
 Options can be reviewed with:
 
 ```shell
-./op --help
+./bin/op-node --help
 ```
 
 To start syncing the rollup:
@@ -24,18 +37,13 @@ To start syncing the rollup:
 Connect to at least one L1 RPC and L2 execution engine:
 
 - L1: use any L1 node / RPC (websocket connection path may differ)
-- L2: run the Optimism fork of geth: <https://github.com/ethereum-optimism/op-geth>
-
-Initialize the L2 chain with a `genesis.json` chain spec like L1, with the Merge fork activated from genesis.
-
-Specify genesis details:
-
-- L1 number / hash: starting-point of L2 chain inputs
-- L2 genesis hash: to confirm we are building on the correct L2 genesis
+- L2: run the Optimism fork of geth: [`op-geth`](https://github.com/ethereum-optimism/op-geth)
 
 ```shell
 # websockets or IPC preferred for event notifications to improve sync, http RPC works with adaptive polling.
 op \
   --l1=ws://localhost:8546 --l2=ws//localhost:9001 \
-  --genesis.l1-num=.... --genesis.l1-hash=..... --genesis.l2-hash=....
+  --rollup.config=./path-to-network-config/rollup.json \
+  --rpc.addr=127.0.0.1 \
+  --rpc.port=7000
 ```