Fix #278, implement raw_prompt_skippable for Select

inquire/src/prompts/select/mod.rs

@@ -325,6 +325,26 @@ where
         }
     }
 
+    /// Parses the provided behavioral and rendering options and prompts
+    /// the CLI user for input according to the defined rules.
+    ///
+    /// Returns a [`ListOption`](crate::list_option::ListOption) containing
+    /// the index of the selection and the owned object selected by the user.
+    ///
+    /// This method is intended for flows where the user skipping/cancelling
+    /// the prompt - by pressing ESC - is considered normal behavior. In this case,
+    /// it does not return `Err(InquireError::OperationCanceled)`, but `Ok(None)`.
+    ///
+    /// Meanwhile, if the user does submit an answer, the method wraps the return
+    /// type with `Some`.
+    pub fn raw_prompt_skippable(self) -> InquireResult<Option<ListOption<T>>> {
+        match self.raw_prompt() {
+            Ok(answer) => Ok(Some(answer)),
+            Err(InquireError::OperationCanceled) => Ok(None),
+            Err(err) => Err(err),
+        }
+    }
+
     /// Parses the provided behavioral and rendering options and prompts
     /// the CLI user for input according to the defined rules.
     ///