Optimized language, themes, colors.

Added splashscreen, SplashActivity.

app/src/main/java/com/fatapp/oxygentoolbox/SplashActivity.java

@@ -1,14 +1,24 @@
 package com.fatapp.oxygentoolbox;
 
+import android.annotation.SuppressLint;
+import android.content.Intent;
 import android.os.Bundle;
 
 import androidx.appcompat.app.AppCompatActivity;
+import androidx.core.splashscreen.SplashScreen;
 
+@SuppressLint("CustomSplashScreen")
 public class SplashActivity extends AppCompatActivity {
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
+        // Handle the splash screen transition.
+        SplashScreen splashScreen = SplashScreen.installSplashScreen(this);
+
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_splash);
+
+        startActivity(new Intent(getApplicationContext(), MainActivity.class));
+        finish();
     }
 }