It does not matter if you open a PR if the project is not open to that solution. You can't just add any random thing to Postgres as an outsider. You first have to convince the people in the project that X is a good thing to add and only after that does it make sense to actually implement it (and even then unlikely that OpenAI has a developer on staff with enough Postgres experience to actually write it. More likely they will then just sponsor a dev from the project).