dvDocsBrowserSource function
The document the build wrote, fetched from base beside it.
base is where the site is mounted rather than where the document is: the
mount is the project's to move, and /docs/ or /__docs should both work
without this repeating either.
Implementation
DVDocsSource dvDocsBrowserSource({String base = '/'}) => () async =>
dvDocsDecode(await platform.dvDocsReadPayload(dvDocsAt(base)));