Problem: We had MediaWiki:Randomlexeme locally defined on Wikidata. This makes it difficult to translate the message, as each translation must be manually included on a subpage by an administrator, and forces external installations to do the same locally.
The message was renamed to MediaWiki:Wikibase-lexeme-randomlexeme and added to the Wikidata.org extension so that it could be translated, but the messages are still not available to external installations.

Screenshots/mockups:

Acceptance criteria:

• The Wikibase Lexeme extension introduces the interface message MediaWiki:Wikibase-lexeme-randomlexeme by default.
• The default content of MediaWiki:Wikibase-lexeme-randomlexeme in English is Random Lexeme.

Open questions:

• The name of this message is based on that of MediaWiki:Randompage, but a different one could be defined.