feat: Adds WarningButton component

[rllina]

Description

• Adds a "WarningButton" sub-component of "Button", in the pattern of the PrimaryButton and DangerButton.
• Uses the "warning" yellow color #ffbb00

Changes include

• [ ] breaking change: a change that is not backwards-compatible and/or changes current functionality
• [ ] fix: a non-breaking change that solves an issue
• [x] feature: a non-breaking change that adds functionality
• [ ] chore: contains no changes affecting the library, such as documentation or test updates

Feature checklist

• [x] Appropriate tests have been added
• [x] Documentation has been updated
• [x] Accessibility has been considered

[haideralsh]

@rllina for work that involves adding a new component or alters an existing one visually we usually ask for a designer to approve this work. I am not sure if this was approved by the designer on you team. If not I will let @nikola-nulogy take a look at it.

[rllina]

Closing this pr after discussing options with @nikola-nulogy