ctest: Update docs for the type rename methods

See #4996

Author: cbarrick

ctest/src/generator.rs

@@ -927,6 +927,10 @@ impl TestGenerator {
     ///
     /// # Examples
     ///
+    /// This method can be used to remove the `struct` keyword from types in the
+    /// generated tests. For example, the code below will generate tests for
+    /// `timeval_t` rather than `struct timeval`.
+    ///
     /// ```no_run
     /// use ctest::TestGenerator;
     ///
@@ -950,6 +954,10 @@ impl TestGenerator {
     ///
     /// # Examples
     ///
+    /// This method can be used to remove the `union` keyword from types in the
+    /// generated tests. For example, the code below will generate tests for
+    /// `__T1Union` rather than `union T1Union`.
+    ///
     /// ```no_run
     /// use ctest::TestGenerator;
     ///