[New Extension]: pg_partman

### Is there an existing issue for this extension request?

- [x] I have searched for an existing issue, and could not find a duplicate request.

### Extension Name

pg_partman

### Project Repository URL

https://github.com/pgpartman/pg_partman

### Extension Website URL (Optional)

https://github.com/pgpartman/pg_partman

### Short Description

pg_partman is a partition management extension for PostgreSQL. It automates the creation and maintenance of time-based or serial/integer-based table partition sets, including automatic creation of future partitions and optional cleanup of old ones.

### Main LICENSE Link

https://github.com/pgpartman/pg_partman/blob/master/LICENSE

### License Compliance

- [x] The extension's license (linked above) complies with the list of allowed licenses.

### Known Dependent Extensions

None

### Component Owner and Maintenance Commitment

- [x] I/My organization commit to becoming the Component Owner and maintaining the extension image in the future.

### Additional Notes (Optional)

A PR implementing this extension is already open: #159

# | Title | Status
-- | -- | --
#159 | Added pg_partman extension (PR by egkristi) | Open (in progress, review required)
#9 | feat: add pg_partman extension (PR by jcpunk) | Closed (abandoned)
#8 | [feature] extension image for pgpartman | Closed (not planned)

### GitHub Handles of Component Owners

@egkristi

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct