Add hardware keyboard detection on Android

source/funkin/external/android/java/funkin/util/KeyboardUtil.java

@@ -0,0 +1,14 @@
+package funkin.util;
+
+import org.haxe.extension.Extension;
+
+public class KeyboardUtil
+{
+  public static boolean isKeyboardConnected()
+  {
+    if (Extension.mainContext == null) return false;
+
+    // KEYBOARD_UNDEFINED = 0, KEYBOARD_NOKEYS = 1
+    return Extension.mainContext.getResources().getConfiguration().keyboard > 1;
+  }
+}