Add mosaics for Belize

[CharliePlett]

Hi, I would like these mosaics added to the Belize bbox.

Belize DOS 1990 https://mapwarper.net/layers/2505
Belize DOS 1973-76 https://mapwarper.net/layers/2488
British Honduras DOS 1965-66 https://mapwarper.net/layers/2487