Create structure for entities.

src/parser/mod.rs

@@ -7,6 +7,7 @@ mod drawer;
 mod dynamic_block;
 mod element;
 mod element_parser;
+mod entity;
 mod exiting;
 mod fixed_width_area;
 mod footnote_definition;
@@ -70,6 +71,7 @@ pub use lesser_element::VerseBlock;
 pub use object::AngleLink;
 pub use object::Bold;
 pub use object::Code;
+pub use object::Entity;
 pub use object::Italic;
 pub use object::Object;
 pub use object::OrgMacro;