Rust grammar: Doc comments in Rust are actually not comments, therefore shouldn't be marked as such

[alexr00]

From @KSXGitHub

Comments are pieces of code that is usually ignored and can be placed anywhere. Doc comments in most languages are usually ignored by the compiler/interpreter. But Rust's so-called "doc comments" are different from normal comments:

• Under every outer doc (/// ..., /** ... */, or #[doc = "..."]) must be a language item. Otherwise, it is a syntax error.
• Every inner doc (//! ..., /*! ... */, or #![doc = "..."]) must be placed within a language item. Otherwise, it is a syntax error.
• Doc comment is just syntactic sugar for the #[doc] attribute.

Suggestion

Doc comment in Rust is a flavor of Markdown, therefore it should be highlighted as a Markdown code snippet.