[Postgres] [Adding extension]: Add support for TimescaleDB extension

### Required Terms

- [X] I agree to follow this project's [Code of Conduct](https://github.com/heroku/roadmap/blob/main/CODE_OF_CONDUCT.md)
- [X] I have read and accept the [Salesforce Program Agreement](https://www.salesforce.com/company/program-agreement/)

### What service(s) is this request for?

Postgres

### Tell us about what you're trying to solve. What challenges are you facing?

We are most likely using [TimescaleDB](https://www.timescale.com/) which, currently, will require us to move off of Heroku Postgres which we *really* don't want to do. Could this extension be supported?