waitForJS doesn't work like Webdriver

On Webdriver I have something like that and it works:
`$I->waitForJS("return typeof App !== 'undefined';");`

But with playwright I have an error:
```
page.evaluate: SyntaxError: Illegal return statement
at eval ()
at UtilityScript.evaluate (:234:30)
at UtilityScript. (:1:44)
```

I tried different value but always an error:
`$I->waitForJS("return typeof App !== 'undefined'");`
`$I->waitForJS("typeof App !== 'undefined';");`
`$I->waitForJS("() => typeof App !== 'undefined'");`

從模組的 waitForJS 入口點開始，使用 issue 中的三個表達式重現回報的 page.evaluate SyntaxError。比較預期的 Webdriver 相容輸入與目前的行為；確立受支援的 waitForJS 形式並由回歸測試涵蓋後即完成。

由索引模型根據 Issue 內容生成。