Add Custom CSS Properties for Border Radius, Style, and Color to bl-button

[MehmetCanBOZ]

Description
In split button design Figma, we need to add some CSS custom properties for borders to match with the design.

This issue aims to enhance the bl-button component's styling flexibility by introducing three new CSS custom properties:

• --bl-button-border-radius
• --bl-button-border-style
• --bl-button-border-color

These properties will allow developers to more easily customize the appearance of bl-button components to fit the design requirements of their projects without modifying the component's internal CSS or structure.

[erbilnas]

We don't need these attributes because we already have four styles: Default, Neutral, Success, and Danger. We want to enforce strictness for now in order to maintain consistency within the design system.

[MehmetCanBOZ]

• Is it possible to change the border radius of buttons?

• For border style, in the secondary type of split button, the primary button and dropdown button are adjacent and to avoid overlapping borders each other, I think that if I give the "none" left border style of the dropdown button It solves the issue.

• for border color, in the disabled type of split button, there is a divider between the primary button and the dropdown button. I think that if I give the specific border color to the right border of the split button It solves the issue.

You are right, maybe I can add a divider for the last one, but for the other ones, we can talk if they are necessary or not.

[erbilnas]

• No, it isn't.
• The border style shouldn't be changed by the developer, so I believe your solution is appropriate.
• The button and the dropdown handler each have separate disabled attributes, so they should be considered as three different scenarios.

[erbilnas]

You could consider one of them as the new button inherited from our bl-button, while the other is an already existing component of bl-dropdown.