character substitutions

we would like to use a tool such as importas but would like to enforce that we strip underscores from the alias name.

an example would be for:

```
import "path/to/some_package/proto/some_proto_name"
```
to be enforced to be aliased as `someprotonamepb`.

I don't think this is currently possible with importas. Would this be something that could be supported?