This allows common metadata to be shared across masterlists in a
'prelude' YAML file that is then injected into a masterlist when it is
loaded. Masterlist metadata can then reference anchors within the
prelude to make use of those common metadata.
The prelude file will be version controlled in a separate Git
repository, so the masterlist update functions also apply to managing
its versioning.
Rewrite it as reStructuredText so that it can be hosted alongside the
API documentation on Read The Docs, which allows linking to WIP syntax
documentation.