Support counter set in plain list items.

org_mode_samples/greater_element/plain_list/counter_set.org

@@ -0,0 +1,2 @@
+3. [@3] foo
+4. bar

src/compare/diff.rs

@@ -735,6 +735,8 @@ fn compare_plain_list_item<'s>(
         contents_status,
     )?);
 
+    // TODO: compare :bullet :checkbox :counter :pre-blank
+
     Ok(DiffResult {
         status: this_status,
         name: emacs_name.to_owned(),

src/parser/plain_list.rs

@@ -147,6 +147,11 @@ pub fn plain_list_item<'b, 'g, 'r, 's>(
         Into::<&str>::into(bull) != "*" || indent_level > 0
     })(remaining)?;
 
+    let (remaining, _maybe_counter_set) =
+        opt(tuple((space1, tag("[@"), counter, tag("]"))))(remaining)?;
+
+    // TODO: parse checkbox
+
     let (remaining, maybe_tag) = opt(tuple((
         space1,
         parser_with_context!(item_tag)(context),