Use metadata from try-matrix-now

Now that https://matrix.org/docs/projects/try-matrix-now.html has a whole new fresh look and a dedicated maintainer, it would be great that matrix.to uses the same metadata that try-matrix-now does. I might even dare say that metadata for try-matrix-now could be extended with `*_url` and `*_instructions` entries used by matrix.to, and both projects use metadata from the same repo.

Start by comparing the metadata used by try-matrix-now with the metadata consumed by matrix.to. Trace how each project obtains and uses these entries, including the proposed *_url and *_instructions fields; done means matrix.to uses the shared metadata source consistently.

Written by the indexing model from the issue text.