[MRG] update readme for 0.4.0

[HuaizhengZhang]

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PR Type

documentation

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Description

• Updated the README to include a new milestone for the release of version 0.4.0.
• Highlighted new command-line interfaces (CLIs) such as MLE report, MLE kaggle, and MLE integration.
• Mentioned the introduction of new models like Mistral.

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Changes walkthrough 📝

	Relevant files
Documentation	README.md Add milestone for version 0.4.0 release in README                README.md Added a new milestone for the release of version 0.4.0. Mentioned new CLIs and models introduced in version 0.4.0. +1/-0

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