Update ECOSYSTEM.md to reflect updated partnerships (#29527)

Summary:
To help reflect how we've collectively been thinking about partnership and engagement on React Native, this change moves Facebook into the Partners list alongside other partners like Expo, Microsoft, and others. This change helps establish that the React Native teams across Facebook & Microsoft are one big happy family :)

## Changelog

<!-- Help reviewers and the release process by writing your own changelog entry. For an example, see:
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[General] [Changed] - Updated ECOSYSTEM.md to reflect partnerships between Facebook, Microsoft, and others

Pull Request resolved: #29527

Test Plan: N/A - document change

Reviewed By: cpojer

Differential Revision: D22845420

Pulled By: TheSavior

fbshipit-source-id: b3393c8749efc924b27d101d0513ae55eba55270

ECOSYSTEM.md

@@ -10,14 +10,15 @@ There are three types of stakeholders:
 
 ## Partners
 
-Partners are companies that are significantly invested in React Native and have been for years. Informed by their use of React Native, they push for improvements of the core and/or the ecosystem around it. Facebook's partners think of React Native as a product: they understand the trade offs that the project makes as well as future plans and goals. Together we shape the vision for React Native to make it the best way to build applications.
+Partners are companies that are significantly invested in React Native and have been for years. Informed by their use of React Native, they push for improvements of the core and/or the ecosystem around it. Partners think of React Native as a product: they understand the trade offs that the project makes as well as future plans and goals. Together we shape the vision for React Native to make it the best way to build applications.
 
-Our current set of partners include Callstack, Expo, Infinite Red, Microsoft and Software Mansion. Many engineers from these companies are core contributors, and their partner responsibilities also include:
+React Native's current set of partners include Callstack, Expo, Facebook, Infinite Red, Microsoft and Software Mansion. Many engineers from these companies are core contributors, and their partner responsibilities also include:
 
 * **[Callstack](https://callstack.com/):** Manages releases, maintains the [React Native CLI](https://github.com/react-native-community/react-native-cli) and organizes [React Native EU](https://react-native.eu/)
 * **[Expo](https://expo.io/):** Builds [expo](https://github.com/expo/expo) on top of React Native to simplify app development
+* **[Facebook](https://opensource.facebook.com):** Oversees the React Native product and maintains the [React Native core repo](https://reactnative.dev/) 
 * **[Infinite Red](https://infinite.red/):** Maintains the [ignite cli/boilerplate](https://github.com/infinitered/ignite), organizes [Chain React Conf](https://infinite.red/ChainReactConf)
-* **[Microsoft](https://www.microsoft.com/en-gb/):** Develops [React Native Windows](https://github.com/Microsoft/react-native-windows) for the Universal Windows Platform (UWP)
+* **[Microsoft](http://aka.ms/reactnative):** Develops [React Native Windows](https://github.com/Microsoft/react-native-windows) and [React Native macOS](https://github.com/microsoft/react-native-macos) for building apps that target Windows and macOS
 * **[Software Mansion](https://swmansion.com/):** Maintain core infrastructure including JSC, Animated, and other popular third-party plugins.
 
 In terms of open source work, pull requests from partners are commonly prioritized. When you are contributing to React Native, you'll most likely meet somebody who works at one of the partner companies and who is a core contributor: