Removed need for width and size + added cusomization options

[SeriousMonk]

This PR removes the need to pass width and height arguments to FlutterPwValidator. The widget will now always fill the width and use only as much height as necessary for the widget.

Added a few customization options:

1. textStyle argument to allow for easy text style customization of the bullet points
2. padding argument to apply padding to the entire widget in order to allow devs to adapt this widget to their text fields (eg if the textfield has border radius)
3. showValidationBar and showValidationText flags allow to decide whether to show the validation bar and/or the validation bullet points
4. ``validationBarThickness``` allow to increase or decrease the thickness of the validation bar

Also updated the ValidationTextWidget to show a 'x' or check icon instead of the bullet in the bullet points.

Example project has been updated to reflect these changes.

[ArefMozafari]

Thanks
Please update readme also

[Deatsilence]

This PR removes the need to pass width and height arguments to FlutterPwValidator. The widget will now always fill the width and use only as much height as necessary for the widget.

Added a few customization options:

1. textStyle argument to allow for easy text style customization of the bullet points
2. padding argument to apply padding to the entire widget in order to allow devs to adapt this widget to their text fields (eg if the textfield has border radius)
3. showValidationBar and showValidationText flags allow to decide whether to show the validation bar and/or the validation bullet points
4. ``validationBarThickness``` allow to increase or decrease the thickness of the validation bar

Also updated the ValidationTextWidget to show a 'x' or check icon instead of the bullet in the bullet points.

Example project has been updated to reflect these changes.

İt was so neccesary. İf I didn't see this issue, I'd have added TextStyle property :)

[ArefMozafari]

Hi again
First, thanks for the time.

Second, I was thinking about an useful refactor would be moving all the configuring properties of the initializer to a separate class (As the growth of the project options). Something like FlutterPwValidatorOptions or FlutterPwValidatorConfigs.
This way the caller code can be more shorter and readable.

What do you think?
Please let me know if you would like to do it yourself.