Added grammar of comments
# Comments
+> **<sup>Lexer</sup>**
+> LINE_COMMENT :
+> &nbsp;&nbsp; `//` ~[\n\r]*
+>
+> BLOCK_COMMENT :
+> &nbsp;&nbsp; `/*` (BLOCK_COMMENT | .)* `*/`
+>
+> OUTER_DOC_LINE_COMMENT :
+> &nbsp;&nbsp; `//!` ~[\n\r]*
+>
+> OUTER_DOC_BLOCK_COMMENT :
+> &nbsp;&nbsp; `/*!` (OUTER_DOC_BLOCK_COMMENT | .)* `*/`
+>
+> INNER_DOC_LINE_COMMENT :
+> &nbsp;&nbsp; `///` ~[\n\r]*
+>
+> INNER_DOC_BLOCK_COMMENT :
+> &nbsp;&nbsp; `/**` (INNER_DOC_BLOCK_COMMENT | .)* `*/`
+
Comments in Rust code follow the general C++ style of line (`//`) and
block (`/* ... */`) comment forms. Nested block comments are supported.
