feat(types): add TypeConversionFunc in common.go (main)

Author: rayakame

internal/types/common.go

@@ -0,0 +1,5 @@
+package types
+
+import "github.com/sqlc-dev/plugin-sdk-go/plugin"
+
+type TypeConversionFunc func(req *plugin.GenerateRequest, col *plugin.Column) string