Recommend pretty-format library provided by jest

I was going through the testing recipes and noticed that the documentation recommends a npm module for pretty printing HTML for snapshot: https://reactjs.org/docs/testing-recipes.html#snapshot-testing.

In this example, we render a component and format the rendered HTML with the pretty package, before saving it as an inline snapshot...

The package is this: https://www.npmjs.com/package/pretty. There is another, imo stronger candidate to replace this package, which is pretty-format. Why would this be better? Its part of jest and the example code in the documentation is already using jest. Therefor it would be better to recommend a dependency from a source that the reader is already more likely to be using other dependencies from (which in this case is jest).

You can pretty print HTML with pretty-format like so:

import prettyFormat from 'pretty-format';

const pretty = (dom: HTMLElement): string => {
  return prettyFormat(
    dom,
    {
      plugins: [ prettyFormat.plugins.DOMElement ]
    }
  )
}

...

expect(
  pretty(container)
).toMatchInlineSnapshot(); /* ... gets filled automatically by jest ... */

開啟測試配方文件中的 Snapshot Testing 區段，將其中目前對 pretty package 的推薦與 Jest 的 pretty-format package 進行比較。更新推薦和範例以使用提議的 package，然後驗證範例仍與 Jest snapshot testing 保持一致，且頁面不再推薦 pretty。