v0.38.1 — importers.md loses the empty third column

The external flag had its own column, which is blank on every row whenever all
importers are your own -- the common case for a personal library, and one that
reads as a broken table rather than as 'no strangers here'.

Two columns now, with the mark inline in the repository cell so it shows only on
rows it describes. The external count is still stated above the table.