Check that second parameter of Tonic.add is a kebab-case string (if provided)

[chicoxyzzy]

the regex is ^[a-z]+(-[a-z]+)*$

[mahtabhnp]

Hi, I’m interested in working on this issue. Could you please assign it to me? This will be my first contribution, and I’m excited to get started. Let me know if there are any specific guidelines or steps I should follow.

Thank you! @chicoxyzzy