Since #1189, Czech is a complete catalog: every menu string, tl! literal
and status or error message has a cs row, and the i18n tests check it.
cs.tsv gets the rows that the other complete catalogs have for Import
Shortcut Set and its commands: 35 strings, the two plurals with one, few
and other forms, and the two error messages. Shortcut and the Imported
message already have cs rows on main, so they are not repeated. The rows
are placed after the Keyboard Shortcuts… row.