[ctor] adds fn value for examples to work

idioms/ctor.md

@@ -24,6 +24,11 @@ impl Second {
     pub fn new(value: u64) -> Self {
         Self { value }
     }
+
+    /// Returns the value in seconds.
+    pub fn value(&self) -> u64 {
+        self.value
+    }
 }
 ```
 
@@ -44,6 +49,13 @@ pub struct Second {
     value: u64
 }
 
+impl Second {
+    /// Returns the value in seconds.
+    pub fn value(&self) -> u64 {
+        self.value
+    }
+}
+
 impl Default for Second {
     fn default() -> Self {
         Self { value: 0 }
@@ -67,6 +79,13 @@ like they do with `Second`:
 pub struct Second {
     value: u64
 }
+
+impl Second {
+    /// Returns the value in seconds.
+    pub fn value(&self) -> u64 {
+        self.value
+    }
+}
 ```
 
 **Note:** When implementing `Default` for a type, it is neither required nor