enable AND search (rust-lang#1607)

Author: tshepang

Diff for: book.toml

@@ -18,6 +18,9 @@ git-repository-url = "https://github.com/rust-lang/rustc-dev-guide"
 edit-url-template = "https://github.com/rust-lang/rustc-dev-guide/edit/master/{path}"
 additional-js = ["mermaid.min.js", "mermaid-init.js"]
 
+[output.html.search]
+use-boolean-and = true
+
 [output.html.fold]
 enable = true
 level = 0