(More) strongly typed templates

[mmkal]

It'd be nice to use the type from the root migrator object, with information about the context type etc., rather than just import('umzug').Migration.

i.e. something like:

/** @type {typeof import('../your-migrator.js').umzug._types.migration} */
export const up = async params => {}

/** @type {typeof import('../your-migrator.js').umzug._types.migration} */
export const down = async params => {}