Add explicit react-native-screens dependency to the TestApp

[russelarms]

Things to consider before you submit the PR:

• Has CHANGELOG.md been updated?
• Are tests passing locally?
• Are the files formatted correctly?
• Did you test your change with either the sample apps that are included in the repository or with a blank app that uses your change?

Description

react-navigation-tabs package has react-native-screens as a peerDependency, which means it is not downloaded automatically when using npm i. It used to work because react-native-screens was required by react-navigation/native@3.3.0

"@react-navigation/native": {
"version": "3.3.0",
"resolved": "https://registry.npmjs.org/@react-navigation/native/-/native-3.3.0.tgz",
...
"requires": {
"hoist-non-react-statics": "^3.0.1",
"react-native-safe-area-view": "^0.13.0",
"react-native-screens": "^1.0.0 || ^1.0.0-alpha"
},

But react-navigation/native@3.6.5 doesn't have an explicit dependency on react-native-screens anymore:

"@react-navigation/native": {
"version": "3.6.5",
"resolved": "https://registry.npmjs.org/@react-navigation/native/-/native-3.6.5.tgz",
...
"requires": {
"hoist-non-react-statics": "^3.3.2",
"react-native-safe-area-view": "^0.14.8"
},

Related PRs or issues

AB#78100

[MatkovIvan]

It looks like revert of #806

[russelarms]

@MatkovIvan It is needed anyway, without it, the app won't build.
The difference between the two is that DemoApp uses RN 0.59 and TestApp uses RN 0.61, they use different build flows.
It was linked the wrong way on DemoApp, that's why we applied #806