feat(share-intent): improve type safety and initialization order

- Change return type from `SharePayload | null` to `SharePayload | undefined` in TypeScript interface for better type safety
- Move initialization block after method definitions for better code organization
- Add NullType import for Android implementation
- Maintain same functionality while improving code structure and type consistency

Author: SolankiYogesh

android/src/main/java/com/margelo/nitro/nitroshareintent/NitroShareIntent.kt

@@ -25,6 +25,7 @@ import java.io.FileOutputStream
 import java.util.Date
 import androidx.core.net.toUri
 import com.facebook.react.bridge.ActivityEventListener
+import com.margelo.nitro.core.NullType
 
 @DoNotStrip
 class NitroShareIntent : HybridNitroShareIntentSpec(), ActivityEventListener{
@@ -46,15 +47,7 @@ class NitroShareIntent : HybridNitroShareIntentSpec(), ActivityEventListener{
     }
   }
 
-  init {
-    NitroModules.applicationContext.let { ctx->
-      ctx?.addActivityEventListener(this)
-    }
-  }
-
-
   override fun getInitialShare(): Promise<SharePayload?> {
-
     val intent = NitroModules.applicationContext?.currentActivity?.intent
 
     return if (intent != null && isShareIntent(intent)) {
@@ -65,6 +58,12 @@ class NitroShareIntent : HybridNitroShareIntentSpec(), ActivityEventListener{
     }
   }
 
+  init {
+    NitroModules.applicationContext.let { ctx->
+      ctx?.addActivityEventListener(this)
+    }
+  }
+
   override fun onIntentListener(listener: (SharePayload) -> Unit): Double {
     intentListener = listener
     nextListenerId++

src/NitroShareIntent.nitro.ts

@@ -11,6 +11,6 @@ export type SharePayload = {
 
 export interface NitroShareIntent
   extends HybridObject<{ ios: 'swift'; android: 'kotlin' }> {
-  getInitialShare(): Promise<SharePayload | null>;
+  getInitialShare(): Promise<SharePayload | undefined>;
   onIntentListener(listener: (payload: SharePayload) => void): number;
 }