v0.2.1

The C library, prebuilt. No library code changed, and every input parses to
what it did in 0.2.0.

Added

• Prebuilt libdateparsa on every release, for Linux, macOS 13 and later, and
  Windows, each on x86_64 and arm64: one archive per platform with the static
  and the shared library, the header and the licences, plus SHA256SUMS and
  build provenance. Before a release publishes them, each runner OS links the
  C tests against its own platform's archive with the compiler it already
  has, and runs them.