Dubrovnik, on the Yugoslavian coast, was one of the most beautiful places on earth. I spent a week in 1984 filling a sketchbook with drawings of the limestone houses, passageways, courtyards, churches, and gardens within ancient walls that hugged the sea cliffs.This is the sacred place that the Yugoslav Army has just finished shelling to bits - not even for any discernable military reason, but apparently out of spite. Guy Ottewell, Greenville, S.C. Letters are welcome. Only a selection can be published, subject to condensation, and none acknowledged. Please address them to "Readers Write," One Norway St., Boston, MA 02115.