Design source registry repository with metadata patches to merge

[theory]

Building on the patterns developed in #42 & #43, and the CLI in #44, design a Git repository that, when cloned, one can use to build all of its packages. Start with the five packages in #42, those in #43, macOS & Linux, and Postgres versions 13–17. Create a source for v2 META.json files to patch those that come with a distribution, to fix errors and aimed with additional detail.

The repository should just have the metadata and documentation for it to work, and all that should be required to do the work is is the CLI in #44 and the build dependencies.

To that end, it should have metadata or tools to install default build dependencies on all platforms (compiler, make, Rust, etc.)

Done with one can do something like this on macOS and Linux:

1. Install a PostgreSQL version with necessary development support
2. Clone the repository and follow README instructions to get going in just a few minutes:
3. Run a script or command to install any other typical build tools (compiler, make, Rust, pg_prove etc.)
4. Run a script to build a single or all extensions (the latter ideally in parallel up to some number of jobs)
5. Add a new PGXS or pgrx extension by adding a line to a file and optionally a META.json patch file.