feat(template): add Yarn files to .gitignore (#42313)

Summary:
Recently inside React Native Community CLI we added bumping Yarn version inside `init` command, more information here: react-native-community/cli#2134. In this Pull Request I added required rules in `.gitignore` for new projects created.

## Changelog:

[GENERAL] [ADDED] - Add Yarn files to `.gitignore` in template

Pull Request resolved: #42313

Test Plan:
1. Follow [Contributing guide](https://github.com/react-native-community/cli/blob/main/CONTRIBUTING.md) from React Native Community CLI repository to setup locally newest version of CLI.
2. Run this command:

```sh
node /path/to/react-native-cli/packages/cli/build/bin.js init --template path/to/template
```
3. Appropriate should be ignored.

Reviewed By: NickGerleman

Differential Revision: D52907962

Pulled By: cortinico

fbshipit-source-id: f12dce8836e7e94257f8c690434b11227aa46446

packages/react-native/template/_gitignore

@@ -64,3 +64,11 @@ yarn-error.log
 
 # testing
 /coverage
+
+# Yarn
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/sdks
+!.yarn/versions