Allow formatting count value with dart NumberFormat pattern

[shabab477]

Customisability can be increased if there was a way that the number being shown can be formatted from the user side with formatter string. A usual use case for me to add a currency sign after the number, which is not possible write now. A suggestion can be to pass an argument as a Dart NumberFormat pattern and parse the value on the view layer.

Please let me know if this is possible, I would love to contribute by adding an PR if needed. Thanks.