[Feature] Add an input that increments a number contained in a string

[janechu]

Add an input that has advanced keyboard control and treats numbers in strings with incrementing/decrementing numbers.

This input should be created as a configurable web component in fast-tooling which can take an arbitrary modifier that can transform a number during a change event. It should use the form-associated pattern.

An accompanying React component should be added in the fast-tooling-react/src/form as a css-unit.

The units that should work are the w3 recommended units for screen:

• px
• em
• rem
• %

The component should use FormItemBase.

Expect to add:

• softRemove
• renderDefaultValueIndicator
• renderBadge
• renderInvalidMessage

The component should accept:

• All props specified in FormItemCommon
• An optional multipleOf

Example interaction:

1. value is "10px"
2. multipleOf is undefined
3. user pushed the up arrow
4. callback is fired with the value being "11px"

A component to take a cue from for the stying is the number-field.

If the unit is 1, Shift+upArrow is x10

Next steps

• Consult with design on what the desired UI/UX should be, text-field or a number-field and a select with the appropriate units.
• Consider where this can be used in the CSS control

[janechu]

Closed as duplicate of #72