Add info on usage in readme

README.md

@@ -1,3 +1,51 @@
 # type-expand
 
 Utilities to expand TypeScript types shown by IntelliSense in Visual Studio Code.
+
+Inspired by https://stackoverflow.com/a/57683652.
+
+## Installation
+
+```shell
+npm install --save-dev type-expand
+```
+
+## Usage
+
+Commented lines are the results shown in hover info when your cursor hovers over the types.
+
+```typescript
+import type { Expand, ExpandDeep } from "type-expand";
+
+type FooError = { foo: Error };
+type BarError = { bar: Error };
+
+type FooBarError = FooError & BarError;
+// type FooBarError = FooError & BarError;
+
+type ExpandedFooBarError = Expand<FooBarError>;
+// type ExpandedFooBarError = {
+// foo: Error;
+// bar: Error;
+// };
+
+type DeepExpandedFooBarError = ExpandDeep<FooBarError>;
+// type DeepExpandedFooBarError = {
+// foo: {
+// name: string;
+// message: string;
+// stack?: string;
+// };
+// bar: {
+// name: string;
+// message: string;
+// stack?: string;
+// };
+// };
+```
+
+Unlike other utility types, `Expand` and `ExpandDeep` do not transform type in any way.
+
+## See Also
+
+- [`typesafeconfig`](https://github.com/shian15810/typesafeconfig)