Make sure triangle is visible on Safari

[jonandernovella]

This makes sure that the border is also visible on Safari.

Related issue(s) and PR(s)

#260

Type of change

• Bug fix (non-breaking change which fixes an issue)

List of changes made

Updated border style to solid, instead of inset, which makes the button visible on all tested browsers.

Testing

• Checkout this branch and test on a safari web browser.

Definition of Done checklist

• I have made an effort making the commit history understandable
• I have performed a self-review of my own code and commented any hard-to-understand areas
• Tests and lint/format validations are passing
• My changes generate no new warnings