allure plugin for robotframework-seleniumlibrary

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This could be an good example or part of a robot adapter
```python
import allure
from SeleniumLibrary import ScreenshotKeywords
from SeleniumLibrary.base import keyword, LibraryComponent

class AllureSeleniumPlugin(LibraryComponent):

@keyword
def capture_page_screenshot(self, filename='selenium-screenshot-{index}.png'):
path = ScreenshotKeywords(ctx=self.ctx).capture_page_screenshot(filename)
allure.attach.file(path, attachment_type=allure.attachment_type.PNG)
```

```robot
Library SeleniumLibrary plugins=AllureSeleniumPlugin
```

从提议的 Python AllureSeleniumPlugin 示例及其 capture_page_screenshot 入口点开始。检查 Robot Framework Library 设置如何传递 plugins=AllureSeleniumPlugin，然后确定集成所需的范围。Done 应提供一个可用的 SeleniumLibrary 插件，将捕获的页面截图附加到 Allure 报告中。

由索引模型根据 Issue 内容生成。