Postgres built-in type ltree is not supported
### Summary

[ltree](1: https://www.postgresql.org/docs/current/ltree.html) is a trusted extension distributed with postgres

### Steps to reproduce

Create a query or mutation that contains a column/parameter of type ltree

### Expected results

The query or mutation is accessible via graphql

### Actual results

CLI error `Don't understand how to build type for ltree`, query/mutation does not appear in schema

### Additional context

Thread with @benjie on the subject in discord https://discord.com/channels/489127045289476126/1157342633644003429 (wherein it was requested I create this issue)

### Possible Solution

Implement ltree as, basically, a text type. There are domain constraints on the text it will accept, but the main thing is to be able to read and write values of ltree via postgraphile without needed to cast to text.
