chore(docs): add example usage

README.md

@@ -1,3 +1,32 @@
 # projen vitest
 
 [Vitest](https://vitest.dev) component for [projen](https://projen.io) [Node.js](https://nodejs.org/en) projects.
+
+## example usage
+
+- in `.projenrc.ts` import `Vitest` component and create new instance of it:
+
+```ts
+import { awscdk, javascript } from "projen";
+import { Vitest } from "@nikovirtala/projen-vitest";
+
+const project = new awscdk.AwsCdkTypeScriptApp({
+    defaultReleaseBranch: "main",
+    devDeps: ["@nikovirtala/projen-vitest"],
+    jest: false,
+    name: "vitest-example",
+    projenrcTs: true,
+});
+
+new Vitest(project);
+
+project.synth();
+```
+
+- in `*.test.ts` import necessary modules from `vitest`:
+
+```ts
+import { describe, expect, test } from "vitest";
+```
+
+- run tests with `pj test`