Prevent nesting of text markup of the same type.

This greatly reduces the amount of detect element calls that are occurring.

src/context/context.rs

@@ -21,6 +21,9 @@ pub enum ContextElement<'r, 's> {
     /// Stores the name of the current element to prevent directly nesting elements of the same type.
     Context(&'r str),
 
+    /// Stores the name of the current object to prevent directly nesting elements of the same type.
+    ContextObject(&'r str),
+
     /// Indicates if elements should consume the whitespace after them.
     ConsumeTrailingWhitespace(bool),