docs(gas-report): add stdin example to readme (#1831)

packages/gas-report/README.md

@@ -1,6 +1,6 @@
 # Gas Report
 
-Gas reporter for specific lines within forge tests
+Measure and report gas usage within forge tests
 
 Add some reports to your forge tests
 
@@ -10,7 +10,7 @@ import { GasReporter } from "@latticexyz/gas-report/src/GasReporter.sol";
 
 contract ExampleTest is Test, GasReporter {
   function testGas() public {
-    startGasReport("Describe what is being gas-reported on");
+    startGasReport("description of behavior to measure gas for");
     // do something here
     endGasReport();
   }
@@ -23,4 +23,10 @@ Then use the cli command to run tests and save the report:
 pnpm gas-report --save gas-report.json
 ```
 
+Or, if you have your own test command, you can pipe the output to `gas-report --stdin`:
+
+```console
+GAS_REPORTER_ENABLED=true forge test -vvv | pnpm gas-report --stdin
+```
+
 Run `pnpm gas-report --help` for more details.