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'");`

Start at the module's waitForJS entry point and reproduce the reported page.evaluate SyntaxError with the three expressions in the issue. Compare the intended Webdriver-compatible input with the current behavior; done when the supported waitForJS form is established and covered by a regression test.

Written by the indexing model from the issue text.