[Feature] add bleu metric and its test file

[go-with-me000]

Motivation

The task of PR this time is to specifically implement the metric of BLEU. I have completed the implementation of BLEU and provided test files to test functions.

Modification

The bleu code file and the corresponding test file are provided. Simple modifications are made to the code that does not conform to the specification. At the same time, BLEU is added to the document.

Checklist

1. Add bleu metric code
2. Provide test files for bleu
3. Make simple modifications to individual files to conform to the commit standard

[CLAassistant]

All committers have signed the CLA.

[ice-tong]

LGTM with the following comments

[ice-tong]

Please @yhcc @zhouzaida have a look~

[jason102811]

Dear go-with-me000,
First of all, we want to express our gratitude for your significant PR in the MMEval . Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR.
As a valued contributor, we would also like to invite you to join our Special Interest Group (SIG) private channel, where you can share your experiences, ideas, and build connections with like-minded peers.
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Best regards！ @go-with-me000