v0.5.0

Breaking: SSSOM term:, field: and format: identifiers and the mapping_set_id have new URIs.
Regenerate stored SSSOM files with codemeta-drift hub sssom rather than joining them with 0.4.0 output.

Upgrade step: a consumer that validates the mapping export against a vendored schema vendors the 1.4 schema
with the new export, since R paths contain @. Readers that skip formats they don't use read it unchanged.
The hub commands of 0.4.0 and older refuse a 1.4 export, so upgrade codemeta-drift with the file.

Added

• See every crosswalk cell for nine citation and package formats, and why a reviewed mapping changed it, in the
  coverage matrix and on the coverage page.
  codemeta-drift hub coverage writes the matrix as Markdown or JSON. It also lists the CodeMeta crosswalks
  nobody has reviewed, each cell marked as a path, prose, empty or unmatched; --codemeta <checkout> adds them.
• The coverage page checks CodeMeta's main branch every Monday and lists the cells that changed since the pinned tag.
• The mapping export covers BibTeX, Python PKG-INFO, R DESCRIPTION and Julia Project.toml, each cell reviewed
  against CodeMeta's crosswalk. Its schema_version is 1.4, and a path key may now contain @, as in R's
  Authors@R. See the mapping export.

Changed

• SSSOM exports carry mapping-set metadata (title, description, version, curator ORCID and provider), and their
  term, field and format identifiers resolve on the coverage page. See the crosswalk hub.