move Mongoose browser docs to README

Author: vkarpov15

README.md

@@ -1,2 +1,45 @@
-# mongoose-browser
-Mongoose browser build
+# @mongoosejs/browser
+
+Browser-based driver and pre-compiled bundle for running Mongoose in the browser, which supports creating schemas and validating documents in the browser.
+`@mongoosejs/browser` does **not** support saving documents, [queries](http://mongoosejs.com/docs/queries.html), [populate](http://mongoosejs.com/docs/populate.html), [discriminators](http://mongoosejs.com/docs/discriminators.html), or any other Mongoose feature other than creating schemas, defining models, and validating documents.
+
+This package has a pre-built bundle of the browser library, including Mongoose.
+If you're bundling your code with [Webpack](https://webpack.js.org/), you should be able to import Mongoose's browser library as shown below if your Webpack `target` is `'web'`:
+
+```javascript
+import mongoose from 'mongoose';
+```
+
+You can use the below syntax to access the Mongoose browser library from Node.js:
+
+```javascript
+// Using `require()`
+const mongoose = require('@mongoosejs/browser');
+
+// Using ES6 imports
+import mongoose from '@mongoosejs/browser';
+```
+
+## Using the Browser Library {#usage}
+
+Mongoose's browser library is very limited. The only use case it supports is validating documents as shown below.
+
+```javascript
+import mongoose from 'mongoose';
+
+const TestModel = mongoose.model('Test', new mongoose.Schema({
+  name: { type: String, required: true }
+}));
+const doc = new TestModel({});
+// Prints an error because `name` is required.
+console.log(doc.validateSync());
+
+// Alternative syntax, bypassing creating a model.
+const doc2 = new mongoose.Document({}, new mongoose.Schema({
+  name: { type: String, required: true }
+}));
+// Prints an error because `name` is required.
+console.log(doc2.validateSync());
+```
+
+You cannot use Mongoose's browser build to `save()` documents or execute queries.