WB-1675: Implement Combobox component with single selection

[jandrade]

Summary:

This is the first PR associated to the Combobox implementation. It includes the basic structure of the Combobox component with single selection support.

Combobox Implementation Plan:

1. #2216
2. Add Combobox component with Single selection support. [CURRENT]
3. Add multiple selection support to Combobox component.
4. Add autocomplete support to Combobox component.
5. Add async/dynamic support to Combobox component.

Issue: https://khanacademy.atlassian.net/browse/WB-1675

Test plan:

Verify that the new Component component works as expected and that the new documentation is accurate.

/?path=/docs/packages-dropdown-combobox--docs

https://5e1bf4b385e3fb0020b7073c-mzmurnrasq.chromatic.com/?path=/docs/packages-dropdown-combobox--docs

Keyboard navigation:

• Focus on the input field to open the Listbox.
• Use the ArrowDown / ArrowUp keys to navigate through the options.
• Use the Enter key to select an option.
• Use the Escape key to close the Listbox.
• Verify that the selected option is displayed in the input field.

https://github.com/Khan/wonder-blocks/assets/843075/64c47c5e-81f5-4e16-a22a-ccc8fcb7abb5