Implement the new fields for radio target.

src/types/object.rs

@@ -120,6 +120,7 @@ pub struct RegularLink<'s> {
 pub struct RadioTarget<'s> {
     pub source: &'s str,
     pub value: &'s str,
+    pub post_blank: Option<&'s str>,
     pub children: Vec<Object<'s>>,
 }
 
@@ -679,11 +680,15 @@ impl<'s> StandardProperties<'s> for RadioTarget<'s> {
     }
 
     fn get_contents<'b>(&'b self) -> Option<&'s str> {
-        todo!()
+        Some(self.value)
     }
 
     fn get_post_blank(&self) -> PostBlank {
-        todo!()
+        self.post_blank
+            .map(|post_blank| post_blank.chars().count())
+            .unwrap_or(0)
+            .try_into()
+            .expect("Too much post-blank to fit into a PostBlank.")
     }
 }