Improve Code Quality with CSS Mixins for input components

[thrbnhrtmnn]

Description / User story

One way to imrpove our code quality and make the code better readable and maintainable we want to use CSS mixins. A good starting point would be to implement this for all input components.

A good example here would be the blr-form-element element, which we are using in multiple places already.

The benefit is also, that this will help us to be more consistent within our components. When we did #564 , it became clear that we are not as consistent as we want to be.

Requirements / Prerequisites

• none

Acceptance Criteria

• Repeating CSS in input components that can be replaced with CSS Mixins has been identified
• CSS Mixins are implemented for input components
  • blr-form-element is used via mixins
  • foxus-ring is used via mixins
  • ...

Additional information

• We also have other approaches that could lead to the same result, clear direction is not decided yet

Code of Conduct

• I agree to follow this project's Code of Conduct