docs: Update README (#92)

* docs: Update README

* Update code example

README.md

@@ -1,8 +1,8 @@
 # ESLintRC Library
 
-This repository contains the legacy ESLintRC configuration file format for ESLint.
+This repository contains the legacy ESLintRC configuration file format for ESLint. This package is not intended for use outside of the ESLint ecosystem. It is ESLint-specific and not intended for use in other programs.
 
-**Note:** This package is not intended for use outside of the ESLint ecosystem. It is ESLint-specific and not intended for use in other programs.
+**Note:** This package is frozen except for critical bug fixes as ESLint moves to a new config system.
 
 ## Installation
 
@@ -16,14 +16,18 @@ npm install @eslint/eslintrc --save-dev
 yarn add @eslint/eslintrc -D
 ```
 
-## Future Usage
-
-**Note:** This package is not intended for public use at this time. The following is an example of how it will be used in the future.
+## Usage
 
 The primary class in this package is `FlatCompat`, which is a utility to translate ESLintRC-style configs into flat configs. Here's how you use it inside of your `eslint.config.js` file:
 
 ```js
 import { FlatCompat } from "@eslint/eslintrc";
+import path from "path";
+import { fileURLToPath } from "url";
+
+// mimic CommonJS variables -- not needed if using CommonJS
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
 
 const compat = new FlatCompat({
     baseDirectory: __dirname,                // optional; default: process.cwd()