Masterdata client doesn't allow search by keyword

[polishq]

The Masterdata API accepts a _keyword query string which allows you to search in all fields marked as searchable, but there is no way to populate this attribute through the @vtex/api Masterdata client functions.

I would suggest that an optional keyword property be added to the SearchInput object in searchDocuments, searchDocumentsWithPaginationInfo, and scrollDocuments.