create implication two-tone_background -> multicolored_background

Link to implication

Just like two-tone_hair implies its multicolored version, so should this one.

The tag implication two-tone_background -> multicolored_background has been rejected.

Previously discussed in topic #12904

Welp, my fault for not checking better. Gonna cancel this request.

The tag implication two-tone_background -> multicolored_background has been rejected.