fix: set CombBox focusMode to BLUR when focus is outside of the component

[christopherhuii]

Summary

In #901, we ensured that the combo box's focusMode was set to BLUR when a user clicked outside of the component. This is not sufficient for keyboard shortcuts, such as tabbing. When a user tabs through input fields, the focus on the combo box isn't reset.

*I also added an additional story that puts a text input next to the combo box to make it easier for folks to test. Since we've had some issues surrounding focus, I think it'd be good to have for testing.

Related Issues or PRs

#901
#902

How To Test

The form must have at least 2 elements to interact with. I used the combo box and a text input.

1. Fill in the combo box (e.g. type value, select from dropdown, etc.)
2. Use tab to focus the next field
3. Type in the text field

Prior to the fix, the user's focus would be shifted back to the combo box.
After the fix, the user is able to continue typing in the text input

[haworku]

Thanks for the new storybook example - good pattern that we can use in other components too to improve testing. Glad we are making incremental a11y improvements.