add keyboard inset workaround to MainActivity

Should be reverted once https://github.com/flutter/flutter/issues/191156 is fixed

android/app/src/main/kotlin/nexus/federated/nexus/MainActivity.kt

@@ -1,5 +1,40 @@
 package nexus.federated.nexus
 
+import android.os.Build
+import android.os.Bundle
+import android.view.View
+import android.view.WindowInsets
+import android.view.WindowInsetsAnimation
 import io.flutter.embedding.android.FlutterActivity
 
-class MainActivity: FlutterActivity()
+// TODO: Revert this commit once https://github.com/flutter/flutter/issues/191156 is fixed
+class MainActivity: FlutterActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.R) return
+
+        window.decorView.setWindowInsetsAnimationCallback(
+            object : WindowInsetsAnimation.Callback(DISPATCH_MODE_CONTINUE_ON_SUBTREE) {
+                override fun onProgress(
+                    insets: WindowInsets,
+                    runningAnimations: List<WindowInsetsAnimation>,
+                ) = insets
+
+                override fun onEnd(animation: WindowInsetsAnimation) {
+                    if ((animation.typeMask and WindowInsets.Type.ime()) != 0) reapplyInsets()
+                }
+            },
+        )
+    }
+
+    override fun onWindowFocusChanged(hasFocus: Boolean) {
+        super.onWindowFocusChanged(hasFocus)
+        if (hasFocus && Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) reapplyInsets()
+    }
+
+    // Posted so it runs after Flutter has applied any insets it deferred.
+    private fun reapplyInsets() {
+        val view = findViewById<View>(FLUTTER_VIEW_ID) ?: return
+        view.post { view.rootWindowInsets?.let(view::onApplyWindowInsets) }
+    }
+}