First implementation moving over to the new exit matcher class system.

src/parser/exiting.rs

@@ -1,10 +1,11 @@
+#[derive(Debug, Copy, Clone)]
 pub enum ExitClass {
     /// Headlines and sections.
-    Document,
+    Document = 1,
 
     /// Elements who take priority over beta elements when matching.
-    Alpha,
+    Alpha = 20,
 
     /// Elements who cede priority to alpha elements when matching.
-    Beta,
+    Beta = 300,
 }