Update options for styling component inputs

[romaricpascal]

When using the autoselect option, the component renders a hint when the value typed by the user matches the start of a suggestion. The styles of this hint need to match some of the styles of the input the user types in so the texts overlap properly. This PR adds a new hintClasses to complement inputClasses.

It uses the value of inputClasses when left null, but can take its own value if necessary to allow either:

• the styling of the hint on its own
• not styling the hint when stylint the inputClasses (by setting an empty string).

[colinrotherham]

Looking good 🙌

Just the .only() to remove, the docs changes aren't blockers

[colinrotherham]

Looks good to me

Would be ace to see tests for:

1. Class only on input and NOT on the hint
2. Class only on hint and NOT on the input

Just to make sure hintClasses: '' etc are working

[romaricpascal]

Yeah, I think it'd be good to look at how to make it easy to have that kind of tests without cluttering the examples:

• Karma tests don't have a system to wait for the UI to have changed before running assertions like WebDriver IO have
• More tests in WebDriver mean more examples on that example page, which is not ideal either. 😔