v0.38.3 — a zero-importer module is a state, not a failure

The badge was written against one page shape and failed the whole badges job on
the two others pkg.go.dev serves: a module nothing imports (which says 'No known
importers' and gives no count) and one not yet crawled (no section at all).
Because the job is all-or-nothing, that took coverage/version/license down too.

Three outcomes now: a countable page renders the cross-checked number, no known
importers renders 0, anything else renders 'unknown' in grey with a warning.

Unknown is still never rendered as 0 — 'nothing imports this' and 'I could not
tell' are different facts, and on a schedule the second printed as the first
would overwrite a real count.