[fine] Dump CSTs and an example zoo

fine/tests/example_tests.rs

@@ -0,0 +1,8 @@
+use fine::parser::concrete::Tree;
+use pretty_assertions::assert_eq;
+
+fn assert_concrete(tree: &Tree, expected: &str) {
+    assert_eq!(tree.dump(), expected, "concrete syntax trees did not match");
+}
+
+include!(concat!(env!("OUT_DIR"), "/generated_tests.rs"));