finish wasm watcher engine

pkg/watcher/example/sql/transfer_table.sql

@@ -0,0 +1,10 @@
+CREATE TABLE eth.token_transfers (
+  id SERIAL PRIMARY KEY,
+  receipt_id INTEGER NOT NULL REFERENCES eth.receipt_cids (id) ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED,
+  log_index INTEGER NOT NULL,
+  contract_address VARCHAR(66) NOT NULL,
+  src VARCHAR(66) NOT NULL,
+  dst VARCHAR(66) NOT NULL,
+  amount NUMERIC NOT NULL,
+  UNIQUE (receipt_id, log_index)
+);

pkg/watcher/example/sql/transfer_trigger.sql

@@ -0,0 +1,7 @@
+CREATE OR REPLACE FUNCTION transfer_trigger() RETURNS trigger AS
+$BODY$
+BEGIN
+  SELECT *
+
+END;
+$BODY$