add vision section to the README

Author: jshin1394

README.md

@@ -2,6 +2,18 @@
 
 `metrax` is a library with standard eval metrics implementations in JAX.
 
+## Vision
+
+While the [JAX ecosystem](https://docs.jax.dev/en/latest/) is powerful, it currently lacks a core evaluation metrics library. This absence presents challenges for users transitioning from other frameworks like TensorFlow or PyTorch, which offer built-in metrics reporting capabilities.
+
+To address these challenges, we introduced metrax, a standalone JAX model evaluation library that:
+*   Provides essential predefined metrics: Includes metrics commonly used to evaluate various machine learning models (classification, regression, recommendation, and language modeling), with the flexibility to add more in the future.
+*   Leverages existing library as a foundation: Builds upon the robust [CLU](https://github.com/google/CommonLoopUtils) library, ensuring compatibility and consistency in distributed and scaled training environments.
+*   Is accessible to both internal and external developers: With a GitHub-first development strategy and daily synchronization to the internal Google systems.
+*   Is developed on GitHub first and is used by several Google core products.
+
+Please refer to the [readthedocs page](http://metrax.readthedocs.io/) of the library for more information.
+
 ## Installation
 
 Install the package by installing the PyPi release.