Use indexed access types in mappers

### Is your feature request related to a problem? Please describe.

The database typescript generator that I use generates only an object type with each table type accessible via index access. It would just be nice not having to manually create types for this, but instead access them directly.

### Describe the solution you'd like

```
config: {
mappers: {
User: './db-codegen#Tables["user"]',
Book: './db-codegen#Tables["book"]',
}
},
```

### Describe alternatives you've considered

_No response_

### Is your feature request related to a problem? Please describe.

Yes, its reduces the amount of manual creation of types for each individual type.