add link for NEP_Active

Author: zhyan0603

tools/readme.md

@@ -50,3 +50,4 @@
 | `pynep`        | https://github.com/bigd4/PyNEP                 | `PyNEP` is a python interface of the machine learning potential NEP used in GPUMD. |
 | `somd`         | https://github.com/initqp/somd                 | `SOMD` is an ab-initio molecular dynamics (AIMD) package designed for the SIESTA DFT code. The SOMD code provides some common functionalities to perform standard Born-Oppenheimer molecular dynamics (BOMD) simulations, and contains a simple wrapper to the Neuroevolution Potential (NEP) package. The SOMD code may be used to automatically build NEPs by the mean of the active-learning methodology. |
 | `NepTrainKit`  | https://github.com/aboys-cb/NepTrainKit        | `NepTrainKit` is a Python package for visualizing and manipulating training datasets for NEP. |
+| `NEP_Active`   | https://github.com/psn417/NEP_Active           | `NEP_Active` is a python package for building the training set using active learning strategy. It follows the method of Moment Tensor Potential (MTP). |