doc: define "react-native" community condition

PR-URL: #45367
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Jan Krems <jan.krems@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/packages.md

@@ -706,6 +706,9 @@ is provided below to assist with ecosystem coordination.
   the given export. _This condition should always be included first._
 * `"deno"` - indicates a variation for the Deno platform.
 * `"browser"` - any web browser environment.
+* `"react-native"` - will be matched by the React Native framework (all
+  platforms). _To target React Native for Web, `"browser"` should be specified
+  before this condition._
 * `"development"` - can be used to define a development-only environment
   entry point, for example to provide additional debugging context such as
   better error messages when running in a development mode. _Must always be