[BUG] 'browser.new_context' parameter 'locale' accepts any meaningless string

[simon-liebehenschel]

async with async_playwright() as p:
      browser = await p.chromium.launch()
      context = await browser.new_context(locale="foO bAr Spam EGgs")  # <-- NO ERROR HERE

Expected behavior

Accept only adequate Languages Codes. Raise ValueError for any non-existing code.

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Another problem is that nobody knows which strings Playwright accepts.

• 'zh' ?
• 'zh-CN' ?
• 'zh_CN' ?

Ideally, a typing.Literal must be defined with a list of accepted languages' codes.