Quick styling fixes for the current filters

[NoemiOverdijk]

This design has been approved and is ready to be implemented.
You can find more details about the design in the Approved | Patterns file.

---

Since the new filter design is out of scope for the MVP, we want to make the current filtering a bit more user friendly with some (hopefully) quick styling fixes.

Current styling

[NoemiOverdijk]

This design is ready to be reviewed. You can find the design in the For Review | Patterns file.

[HeleenSG]

@NoemiOverdijk I've updated the PR based on your feedback. Which adds:

• Border bottom when the filters are opened
• Moves the chevron to the left

@Rieven I've updated the pr description with the todo's. Which mainly include adding the counter to other filters.

[NoemiOverdijk]

@HeleenSG Looks good to me!