title: Error message showing inside the text form field in Flutter
body: <p>I have implemented a text form field with validation, and it returns the error message but it gets displayed inside the text form field. Is there a way to show it outside the text form field?</p>
  <pre><code>Container(
                                    alignment: Alignment.center,
                                    margin: const EdgeInsets.symmetric(
                                        horizontal: 20),
                                    decoration: BoxDecoration(
                                        color: Colors.grey.withOpacity(0.1),
                                        borderRadius: const BorderRadius.all(
                                            Radius.circular(10))),
                                    child: TextFormField(
                                      autovalidateMode:
                                          AutovalidateMode.onUserInteraction,
                                      controller: _controller,
                                      validator: validatePhone,
                                      textAlignVertical: TextAlignVertical.center,
                                      style: const TextStyle(
                                          color: primaryText,
                                          fontFamily: 'InterMedium',
                                          fontSize: 15),
                                      decoration: const InputDecoration(
                                        counterText: '',
                                        errorStyle: TextStyle(
                                          fontFamily: 'InterMedium',
                                        ),
                                        prefixIcon: Padding(
                                          padding: EdgeInsets.only(
                                              left: 20, right: 15),
                                          child: Icon(
                                            Icons.phone_android_rounded,
                                            color: secondaryText,
                                          ),
                                        ),
                                        hintText: 'Enter mobile number',
                                        hintStyle: TextStyle(
                                          fontFamily: 'InterMedium',
                                          color: secondaryText,
                                        ),
                                        border: InputBorder.none,
                                      ),
                                      cursorColor: secondaryColor,
                                      maxLines: 1,
                                      maxLength: 10,
                                      keyboardType: TextInputType.phone,
                                      textInputAction: TextInputAction.done,
                                    ),
                                  ),
  </code></pre>
  <p>How it is now -</p>
  <p><a href="https://i.stack.imgur.com/wCBN0.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wCBN0.jpg" alt="How it is now" /></a></p>
  <p>How I want it to look like -</p>
  <p><a href="https://i.stack.imgur.com/6wOKn.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/6wOKn.png" alt="enter image description here" /></a></p>