Resolve issue #607 with utils::calcWidthOfInput()

[aiwebb]

Description

This change modifies the utils::calcWidthOfInput() function to transfer paddingLeft and paddingRight from the source input to the test input explicitly, rather than relying on the shorthand property padding.

Motivation and Context

See #607 - shorthand CSS properties are not supported in window.getComputedStyle() except in Chrome (due to a departure from CSS spec in favor of usability).

This results in width being undercounted in Firefox for inputs that use padding.

How Has This Been Tested?

Tested in Chrome and Firefox to confirm padding is now accounted for correctly in both.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[aiwebb]

@jshjohnson - is there anything else I should supply for this?

[jeriah-formio]

@jshjohnson any update on this PR?

[jshjohnson]

Thanks 👍