chore(docs): add readme to jest-types

packages/jest-types/README.md

@@ -0,0 +1,21 @@
+# @jest/types
+
+This package contains shared types of Jest's packages.
+
+If you're a user of Jest and looking for types, you could import `@jest/globals`:
+
+```typescript
+import { describe, it, expect } from '@jest/globals';
+
+describe('my tests', () => {
+  it('works', () => {
+    expect(1).toBe(1);
+  });
+});
+```
+
+If you don't want to import types, you could install the [@types/jest](https://www.npmjs.com/package/@types/jest) package.
+This is not maintained by the Jest team though.
+
+
+See https://github.com/facebook/jest/issues/9972 for more info.