Extension: pgx_ulid

This is a proposal to add support for ULIDs in Postgres using the https://github.com/pksunkara/pgx_ulid extension.

The extension is relatively simple, its <150 LOC (not including tests) written in rust using [pgrx](https://github.com/pgcentralfoundation/pgrx):
https://github.com/pksunkara/pgx_ulid/blob/master/src/lib.rs

My apologies I don't know much about WASM bundling yet, so I probably cant help much porting this to pglite, but if anyone wants to take a stab at it, that'd be awesome!

My use-case is that I have an existing Postgres DB full of ULIDs that I'd like to use on the frontend with PGlite, and it would be great to have matching cross-compatible support for ULIDs in the frontend.