Miscellaneous minor improvements (#2370)

src/control-flow-basics/break-continue/labels.md

@@ -19,3 +19,15 @@ fn main() {
     print!("elements searched: {elements_searched}");
 }
 ```
+
+<details>
+
+- Labeled break also works on arbitrary blocks, e.g.
+  ```rust
+  'label: {
+      break 'label;
+      println!("This line gets skipped");
+  }
+  ```
+
+</details>

src/control-flow-basics/exercise.md

@@ -30,7 +30,7 @@ initial `n`.
   todo!("Implement this")
 }
 
+{{#include exercise.rs:tests}}
+
 {{#include exercise.rs:main}}
-  todo!("Implement this")
-}
 ```

src/control-flow-basics/exercise.rs

@@ -34,6 +34,6 @@ fn test_collatz_length() {
 
 // ANCHOR: main
 fn main() {
-    // ANCHOR_END: main
     println!("Length: {}", collatz_length(11));
 }
+// ANCHOR_END: main