doc(lib): Fix toml snippet in markdown
//!
//! *Things it does not preserve:
//! 1. Different quotes and spaces around the same table key, e.g.
-//! ```toml
+//!
+//! ```text
//! [ 'a'. b]
//! [ "a" .c]
//! [a.d]
//! ```
+//!
//! will be represented as (spaces are removed, the first encountered quote type is used)
-//! ```toml
+//!
+//! ```text
//! ['a'.b]
//! ['a'.c]
//! ['a'.d]
//! ```
+//!
//! 2. Children tables before parent table (tables are reordered, see [test]).
//! 3. Scattered array of tables (tables are reordered, see [test]).
//!
