Add ProGuard rule for hermes (#28571)

Summary:
This adds a ProGuard for `hermes` rule so it does not have to be added by users manually.
https://github.com/facebook/react-native/issues/28270

## Changelog

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[Android] [Added] - ProGuard rule for hermes
Pull Request resolved: https://github.com/facebook/react-native/pull/28571

Test Plan:
1. Create a project with/without hermes.
2. Enable proguard.

Reviewed By: cpojer

Differential Revision: D20947095

Pulled By: hramos

fbshipit-source-id: 79b166ad2dd060f20041d9f5cfe2f794c754843d

ReactAndroid/proguard-rules.pro

@@ -51,6 +51,9 @@
 -dontwarn com.facebook.react.**
 -keep,includedescriptorclasses class com.facebook.react.bridge.** { *; }
 
+# hermes
+-keep class com.facebook.jni.** { *; }
+
 # okhttp
 
 -keepattributes Signature