message: Update tests section in I18n Contribution Guide
  Rewrite the tests section to use locale snapshots.
diff: @@ -872,15 +872,12 @@ Your best guess is to copy `formatDistance` property from another locale and cha
  ### Tests
  -Take `test.js` from existing locale (e.g. `en-US`) and replace the test results with expected values.
  -Don't forget to replace the locale code in the test description:
  +To test locales we use snapshots. See [`en-US` snapshot](https://github.com/date-fns/date-fns/blob/master/src/locale/en-US/snapshot.md) for an example.
  -```javascript
  -// Before
  -describe('en-US locale', function () {
  -// After
  -describe('foo-BAR locale', function () {
  -```
  +To generate snapshots, run `yarn locale-snapshots`. The snapshot for the locale
  +you're working on will appear in the root locale directory (e.g. `src/locales/ru/snapshot.md`).
  +
  +Once you are done with the locale, generate the snapshot and review the output values.
  ## Creating a locale with the same language as another locale
  