<axa-stepper> conveys progress through numbered steps.
The array-valued attribute steps specifies the descriptions of the steps, each step being described by a non-empty label string.
The integer-valued attribute stepActive defines the currently active step.
The numeric attribute stepProgress defines the fraction, to which the UI progress bar extends into the currently active step. Legal values are floating-point numbers between 0 and 1, inclusive (e.g. 0.5).