Allow text markup at the start of a radio target.

src/context/context.rs

@@ -33,6 +33,11 @@ pub(crate) enum ContextElement<'r, 's> {
     /// The value stored is the start of the element after the affiliated keywords. In this way, we can ensure that we do not exit an element immediately after the affiliated keyword had been consumed.
     HasAffiliatedKeyword(HasAffiliatedKeywordInner<'r, 's>),
 
+    /// Indicate the position that we started parsing a radio target.
+    ///
+    /// This value is stored because "<<<" is not a valid prefix for text markup UNLESS it is starting a radio target.
+    StartRadioTarget(OrgSource<'s>),
+
     /// This is just here to use the 's lifetime until I'm sure we can eliminate it from ContextElement.
     #[allow(dead_code)]
     Placeholder(PhantomData<&'s str>),