fix: add delta theming for Forms

[katekozlowska]

Related Issue

Part of #1357

Description

Add theming deltas for Forms

Please check whether the PR fulfills the following requirements

1. The output matches the design specs

• N/A All values are in rem
• N/A Text elements follow the truncation rules
• N/A hover state of the element follow design spec
• N/A focus state of the element follow design spec
• N/A active state of the element follow design spec
• N/A selected state of the element follow design spec
• N/A selected hover state of the element follow design spec
• N/A pressed state of the element follow design spec
• N/A Responsiveness rules - the component has modifier classes for all breakpoints
• N/A Includes Compact/Cosy/Tablet design
• N/A RTL support

2. The code follows fundamental-styles code standards and style

• N/A BEM naming convention is used
• N/A Mixins are used for repeatable code (fd-rtl, fd-ellipsis, fd-flex, fd-selected, fd-focus, ect.)
• N/A A11y support - keyboard support, screenreader support, proper ARIA attributes, etc.
• N/A fd-reset() mixin is applied to all elements
• N/A Variables are used, if some value is used more than twice.
• N/A Checked if current components can be reused, instead of having new code.

3. Testing

• N/A tested Storybook examples with "CSS Resources" normalize option
• N/A tested Storybook examples with "CSS Resources" unnormalize option
• N/A Verified all styles in IE11
• N/A Updated tests

4. Documentation

• N/A Storybook documentation has been created/updated
• N/A Breaking Changes wiki has been updated in case of breaking changes.

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[droshev]

@katekozlowska why did you comment all the points on PR with N/A

[JKMarkowski]

LGTM

[stefanoScalzo]

LGTM