Search one Wolt restaurant or store's menu by keyword

Searches one restaurant's or store's own items by keyword, using Wolt's own in-venue item search. This is the only way to reach the items of a large grocery or retail store: /wolt/restaurant/menu returns those venues' categories with no items, because Wolt itself only loads such an assortment a slice at a time. Matching works across languages, so an English keyword finds locally-named products. Each item carries a name, description, price, dietary tags, image, and -- for packaged retail products -- a barcode, pack size, and per-unit comparison price. A keyword is required; a no-match keyword returns an empty item list rather than an error.