Fixed docs indentation.
//! whitespace = _{ " " }
//! ```
//!
-//! Parsing both `"ab"` and `"a b"` produces the token pairs `c(b(a()))`.
+//! Parsing both `"ab"` and `"a b"` produce the token pairs `c(b(a()))`.
//!
//! #### Expressions
//!
