add speak command?

I'm undecided on whether this functionality would be useful and in line with the simplicity of Logo, but here's the idea:

Have the turtle be able to print text to the screen.

Follow-on considerations for a such a feature include: enable configuring font type & size

该 issue 没有指明文件、测试或入口点。首先明确 speak 命令是否符合项目的简洁性、文本应显示在哪里，以及字体配置是否属于范围；完成时应包括已达成一致的命令行为和相应测试。

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