Incorporate leading zero's when rendering TimerText

[gavination]

Currently, there countdown timer does not render leading zeros in the manner an end user would expect, like 00:00. As soon as there are single digits in the number's representation, the format may look like the following to denote that there are 8 seconds left - 0:8. Fix this to represent a more common format for time representation.

Note:

• Investigate formatting this in XAML as opposed to setting it in the C# event responsible for updating the Text field.

[gavination]

addressed in a much earlier PR