remove the template from react-native package (#45008)

Summary:
Pull Request resolved: #45008

As part of RFC0759, we are moving the template into it's own repository.

## Useful Links:
- [Section in RFC0759](https://github.com/react-native-community/discussions-and-proposals/blob/main/proposals/0759-react-native-frameworks.md#evolving-the-react-native-community-template--cli)
- [Template's new home](https://github.com/react-native-community/template)
- [Versioning discussion](react-native-community/cli#2345)

Changelog: [General][Breaking] removed the template from react-native into react-native-community/template

Reviewed By: cortinico

Differential Revision: D58184276

fbshipit-source-id: 5e52320af55495488587accbe144d11164cea4fd

Author: blakef

packages/react-native/README.md

@@ -0,0 +1,8 @@
+# Where is the template?
+The React Native Template has moved from being shipping inside the [react-native](https://www.npmjs.com/package/react-native) package to it's own package: [@react-native-community/template](https://github.com/react-native-community/template).
+
+## Why has it moved?
+The [React Native Frameworks RFC0759](https://github.com/react-native-community/discussions-and-proposals/blob/main/proposals/0759-react-native-frameworks.md#evolving-the-react-native-community-template--cli) provides background information.
+
+## When was it moved?
+The 0.75 release.