Newly created app fails tests

[ericfrank-stripe]

Describe the bug
Creating a fresh Stripe App and running the test suite with yarn test fails with this:
src/views/App.test.tsx
● Test suite failed to run

● Invalid return value:
  Code transformer's `process` method must return an object containing `code` key
  with processed string. If `processAsync` method is implemented it must return
  a Promise resolving to an object containing `code` key with processed string.

[ericfrank-stripe]

Jest version 28.0.0 just came out, and it looks like ts-jest is lagging behind (see kulshekhar/ts-jest#3453). To fix this, change the jest version in package.json to 27.5.1. We will pin this version in the CLI.

[ericfrank-stripe]

This is fixed for newly created apps in the latest version of the CLI. To upgrade your CLI, run stripe plugin upgrade apps.