Added external binary representation for vector type

sql/copy.sql

@@ -0,0 +1,15 @@
+SET client_min_messages = warning;
+CREATE EXTENSION IF NOT EXISTS vector;
+
+CREATE TABLE t (val vector(3));
+INSERT INTO t (val) VALUES ('[0,0,0]'), ('[1,2,3]'), ('[1,1,1]'), (NULL);
+
+CREATE TABLE t2 (val vector(3));
+
+\copy t TO '/tmp/data.bin' WITH (FORMAT binary)
+\copy t2 FROM '/tmp/data.bin' WITH (FORMAT binary)
+
+SELECT * FROM t2 ORDER BY val;
+
+DROP TABLE t;
+DROP TABLE t2;