add basic signature in template (#22665)

Summary:
https://github.com/react-native-community/react-native-cli/issues/38.
add basic signature in template.
Signature file is the same as RNTester.
pass all current ci.
 [Android] [Feature] - add basic signature in template
Pull Request resolved: https://github.com/facebook/react-native/pull/22665

Differential Revision: D13490480

Pulled By: hramos

fbshipit-source-id: 9d0ca4debde2ddbde0d4a611b9b41fc24235314a

template/android/app/build.gradle

@@ -112,8 +112,22 @@ android {
             include "armeabi-v7a", "x86", "arm64-v8a"
         }
     }
+    signingConfigs {
+        debug {
+            storeFile file('debug.keystore')
+            storePassword 'android'
+            keyAlias 'androiddebugkey'
+            keyPassword 'android'
+        }
+    }
     buildTypes {
+        debug {
+            signingConfig signingConfigs.debug
+        }
         release {
+            // Caution! In production, you need to generate your own keystore file.
+            // see https://facebook.github.io/react-native/docs/signed-apk-android.
+            signingConfig signingConfigs.debug
             minifyEnabled enableProguardInReleaseBuilds
             proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro"
         }

template/android/keystores/_BUCK

@@ -1,8 +0,0 @@
-keystore(
-    name = "debug",
-    properties = "debug.keystore.properties",
-    store = "debug.keystore",
-    visibility = [
-        "PUBLIC",
-    ],
-)

template/android/keystores/debug.keystore.properties

@@ -1,4 +0,0 @@
-key.store=debug.keystore
-key.alias=androiddebugkey
-key.store.password=android
-key.alias.password=android