Updating README generation

[aspctu]

trafficstars

What: Creating a CLI command for readme generation and including the new description from config.yaml in the README.

[linear[bot]]

BT-5102 Automate readme generation of examples in truss repo

We should expose a truss cli command for readme generation and use that in a git hook to auto-generate readmes for all examples under /examples in truss repo.

Also, update the readme to include the description field.

We should also add a header comment to the generated readme, saying that the readme is auto-generated, warn against manual modification and show the command to regenerate the readme.