[Feature Request] Default input value

[VKBobyr]

While it is currently possible to set a default input value by directly setting the positional argument of the Txt widget, the default value only appears after the field is selected, causing a weird jump from an empty to a filled field.

Related but not part of the request, it would also be nice to have a way to have a value implementation alongside the defaultValue, which is similar to HTML's implementation of value and defaultValue.