Add SQL command to view excluded tables

Author: rogerwelin

README.md

@@ -199,6 +199,9 @@ SELECT column_tetris.mode();
 
 -- Exclude a table from validation (e.g., matching an external schema)
 SELECT column_tetris.exclude('legacy_imports');
+
+-- View excluded table-/s
+SELECT * FROM column_tetris.exclusions;
 ```
 
 ### What gets checked