Add migrations to 0.2.8

There aren't any DB changes between 0.2.7 and 0.2.8, so the migration
script from 0.2.7 simply updates the version, and the pgstac.0.2.8.sql
is a copy of 0.2.7 with the version entry updated.

Author: lossyrob

pypgstac/pypgstac/migrations/pgstac.0.2.7-0.2.8.sql

@@ -0,0 +1,6 @@
+SET SEARCH_PATH TO pgstac, public;
+BEGIN;
+
+INSERT INTO migrations (version) VALUES ('0.2.8');
+
+COMMIT;