Add a CLI tool to list all supported CodeMeta terms and document them.

Depends on swh-docs!26 (closed). Resolves #1545 (closed).

Preview:

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Migrated from D1200 (view on Phabricator)

docs/metadata-workflow.rst

@@ -108,3 +108,14 @@ The following sources of intrinsic metadata are supported:
 .. _package.json: https://docs.npmjs.com/files/package.json
 .. _PKG-INFO: https://www.python.org/dev/peps/pep-0314/
 .. _.gemspec: https://guides.rubygems.org/specification-reference/
+
+
+Supported CodeMeta terms
+------------------------
+
+The following terms may be found in the output of the metadata translation
+(other than the `codemeta` mapping, which is the identity function, and
+therefore supports all terms):
+
+.. program-output:: python3 -m swh.indexer.cli mapping list-terms --exclude-mapping codemeta
+    :nostderr: