Configuring Postgres from Docker container

I noticed that for the TimescaleDB Docker image, the TIMESCALEDB_ENABLED environment variable is explicitly set to append 'timescaledb' to "shared_preload_libraries" in the Postgres config.

I'd like to install other Postgres extensions in my own custom Docker image such as pg_stat_monitor or pg_safeupdate which requires overwriting Postgres' config with shared_preload_libraries.

`fly pg config` exists, though I would prefer not to have to manually re-configure my Postgres cluster every time I re-deploy a new one.

Are there any ways to make Postgres configuration changes right from the Docker image and ensure that it persists throughout a deployed Fly.io Postgres cluster?