Add description of fp8 function support in md file

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Description

目前支持FP8 PTQ功能，添加相关的文档介绍以及FP8 PTQ功能使用案例

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 54.42%. Comparing base (65e721e) to head (a3e3862). Report is 148 commits behind head on develop.

:exclamation: Current head a3e3862 differs from pull request most recent head bbfb24a

Please upload reports for the commit bbfb24a to get more accurate results.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #8610 +/- ## =========================================== - Coverage 55.80% 54.42% -1.39% =========================================== Files 620 632 +12 Lines 96642 99475 +2833 =========================================== + Hits 53928 54135 +207 - Misses 42714 45340 +2626 ```

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This Pull Request is stale because it has been open for 60 days with no activity. 当前Pull Request 60天内无活动，被标记为stale。