[DOCS]Add mmengine in readme (#8799)

Author: hewanru-bit

README.md

@@ -350,6 +350,7 @@ This project is released under the [Apache 2.0 license](LICENSE).
 
 ## Projects in OpenMMLab
 
+- [MMEngine](https://github.com/open-mmlab/mmengine): OpenMMLab foundational library for training deep learning models.
 - [MMCV](https://github.com/open-mmlab/mmcv): OpenMMLab foundational library for computer vision.
 - [MIM](https://github.com/open-mmlab/mim): MIM installs OpenMMLab packages.
 - [MMClassification](https://github.com/open-mmlab/mmclassification): OpenMMLab image classification toolbox and benchmark.

README_zh-CN.md

@@ -348,6 +348,7 @@ MMDetection 是一款由来自不同高校和企业的研发人员共同参与
 
 ## OpenMMLab 的其他项目
 
+- [MMEngine](https://github.com/open-mmlab/mmengine): OpenMMLab 深度学习模型训练基础库
 - [MMCV](https://github.com/open-mmlab/mmcv): OpenMMLab 计算机视觉基础库
 - [MIM](https://github.com/open-mmlab/mim): MIM 是 OpenMMlab 项目、算法、模型的统一入口
 - [MMClassification](https://github.com/open-mmlab/mmclassification): OpenMMLab 图像分类工具箱