chore: set library namespace in build script (#2005)

Since AGP 8.0 project namespace must be set inside build script.
It is also the recommended way in Android docs.

It is also recommended, that the package name definition is removed from Android manifest file, but I've had some problems in react-native-screens with RN CLI crashing (as it was expecting the package field to exist) & according to this conversation it'll still be legal to leave package name definition in Android manifest file as long as it exactly matches the value in build script.

android/build.gradle

@@ -39,6 +39,7 @@ def safeExtGet(prop, fallback) {
 
 android {
     compileSdkVersion safeExtGet('compileSdkVersion', 28)
+    namespace "com.horcrux.svg"
 
     // Used to override the NDK path/version on internal CI or by allowing
     // users to customize the NDK path/version from their root project (e.g. for M1 support)