rofl.yaml could specify a schema to have autocomplete

[lukaw3d]

Depending on how often users will manually edit rofl.yaml, it may be worth adding a yaml schema.

But yaml schema support in editors is not as common as json schema support

• vscode needs extension https://marketplace.visualstudio.com/items?itemName=redhat.vscode-yaml
• zed does support it https://zed.dev/docs/languages/yaml

# yaml-language-server: $schema=https://raw.githubusercontent.com/oasisprotocol/cli/...schema.json

This works like "$schema": in json:

• editor marks typos and type errors
• editor autocompletes field names