feature: add leanback for android tv compatiblity

V2rayNG/app/src/main/kotlin/com/v2ray/ang/ui/MainActivity.kt

@@ -613,13 +613,14 @@ class MainActivity : BaseActivity(), NavigationView.OnNavigationItemSelectedList
 //    }
 
     override fun onKeyDown(keyCode: Int, event: KeyEvent): Boolean {
-        if (keyCode == KeyEvent.KEYCODE_BACK) {
+        if (keyCode == KeyEvent.KEYCODE_BACK || keyCode == KeyEvent.KEYCODE_BUTTON_B) {
             moveTaskToBack(false)
             return true
         }
         return super.onKeyDown(keyCode, event)
     }
 
+
     fun showCircle() {
         binding.fabProgressCircle.show()
     }

V2rayNG/app/src/main/kotlin/com/v2ray/ang/util/Utils.kt

@@ -7,6 +7,7 @@ import android.util.Base64
 import java.util.*
 import android.content.ClipData
 import android.content.Intent
+import android.content.pm.PackageManager
 import android.content.res.Configuration.UI_MODE_NIGHT_MASK
 import android.content.res.Configuration.UI_MODE_NIGHT_YES
 import android.net.Uri
@@ -399,5 +400,9 @@ object Utils {
         return URL(url.protocol, IDN.toASCII(url.host, IDN.ALLOW_UNASSIGNED), url.port, url.file)
             .toExternalForm()
     }
+
+    fun isTv(context: Context): Boolean =
+        context.packageManager.hasSystemFeature(PackageManager.FEATURE_LEANBACK)
+
 }