docs: add about section with limitations and reasons (#88)

Author: mrmckeb

README.md

@@ -12,7 +12,8 @@ for [CSS Modules](https://github.com/css-modules/css-modules).
 ## Table of contents
 
 - [typescript-plugin-css-modules](#typescript-plugin-css-modules)
-  - [Table of contents](#table-of-contents)
+  - [Table of contents](#about-this-plugin)
+  - [About this plugin](#table-of-contents)
   - [Installation](#installation)
     - [Importing CSS](#importing-css)
     - [Options](#options)
@@ -28,6 +29,22 @@ for [CSS Modules](https://github.com/css-modules/css-modules).
   - [Troubleshooting](#troubleshooting)
   - [About this project](#about-this-project)
 
+## About this plugin
+
+This plugin provides type information to IDEs and any other tools that work with [TypeScript language service plugins](https://github.com/microsoft/TypeScript/wiki/Writing-a-Language-Service-Plugin#whats-a-language-service-plugin).
+
+At this time, TypeScript does not support plugins during compilation. This means that this plugin cannot:
+
+- provide errors during compilation, or
+- add CSS module support to your project.
+
+For more information, and/or to add support for this feature, see: https://github.com/microsoft/TypeScript/issues/16607.
+
+If you need a different solution, these projects might help:
+
+- For Jest support, see https://www.npmjs.com/package/jest-css-modules-transform (one of a few options).
+- For Webpack configuration, see https://webpack.js.org/loaders/css-loader/#pure-css-css-modules-and-postcss for an example.
+
 ## Installation
 
 To install with Yarn:
@@ -54,6 +71,8 @@ Once installed, add this plugin to your `tsconfig.json`:
 
 If you're using Visual Studio Code, please also follow these [instructions](#visual-studio-code).
 
+As Webpack configurations vary, you may need to provide additional [options](#options) to this plugin to match your project configuration. For Create React App users, this plugin will work without additional configuration.
+
 ### Importing CSS
 
 A default export is always provided for your CSS module.