feat(benchmark): improve benchmarks

- Document the port to view deopt info on.
- Return parse tree, so I can conveniently `console.log()` it if
  desired.

packages/benchmark/README.md

@@ -50,4 +50,5 @@ yarn
 (cd packages/v8-deopt-webapp && yarn build)
 node_modules/.bin/v8-deopt-viewer -i $path_to_v8_log
 (cd v8-deopt-viewer && python3 -m http.server)
+open http://localhost:8000
 ```

packages/benchmark/src/benchmark-table-parser.ts

@@ -9,7 +9,7 @@ const readFile = promisify(fs.readFile);
 
 function parse(source: string) {
   const tokens = [...lex(source)];
-  parseWithTable(table, tokens, grammar, makeNode);
+  return parseWithTable(table, tokens, grammar, makeNode);
 }
 
 async function read(file: string): Promise<string> {