Is your feature request related to a problem? Please describe.
Axis domain padding can be specified as percentage or total value related to the scale itself. However as this setting is often used for aesthetics, it would be useful to specify it as a pixel value.

Describe the solution you'd like
elastic-charts should take a setting like this:

{ padding:  '10px' }

Then it does the calculation of values to pixels and applies the appropriate padding

Describe alternatives you've considered
Theoretically the consumer could do this calculation, but it's cumbersome because the height of the chart has to be tracked to do so.

Additional context
This came up because the comment of the padding property actually specifies it can be a pixel value which is not the case

Checklist

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