fix(component/stars-input): stringify "background-image" parameter to avoid ";" expectation SASS error

[pinguet62]

I have read the contributing guidelines

• [x] Yes
• [ ] No

Does this PR introduce a breaking change?

• [ ] Yes
• [x] No

Describe the changes

I have this following error when c.stars-input is imported: [sass] expected ";". on background-image CSS tag.

I reproduced the error on this minimalist repo: https://github.com/pinguet62/mozaic-starsinput ℹ️ You can find distinct commits.

Other information

Apparently there is an issue between url() and SASS variables and a workaround is to use interpolation. And wrap some SASS variable with #{ } seems fix the problem. I don't know if it's the best solution 😉