Support Gorm-style error checking

Gorm uses non-standard error format to support it's chainable API. It would be nice if there was a way to configure wrapcheck to match a `*.\.Error` regex


```go
tx := tx.Find(&customer)
if tx.Error != nil {
    return nil, tx.Error // wrapcheck should warn here
}


abc := tx.Find(&customer)
if abc.Error != nil {
    return nil, abc.Error // wrapcheck should warn here
}
```