support autofocus for android

android/src/main/java/com/reactnativecommunity/webview/RNCWebViewManager.java

         break;
       case COMMAND_FOCUS:
         root.requestFocus();
+        Context ctx = root.getContext();
+        InputMethodManager imm = (InputMethodManager) ctx.getSystemService(Context.INPUT_METHOD_SERVICE);
+        imm.toggleSoftInput(0, InputMethodManager.HIDE_NOT_ALWAYS);
         break;
       case COMMAND_CLEAR_FORM_DATA:
         root.clearFormData();