Update doc comment for `HttpRequest::app_data` (#1265)

* update doc comment for `HttpRequest::app_data`

* add `no_run` to doc comment

* add `ignore` to doc comment

* Update src/request.rs

Co-Authored-By: Yuki Okushi <huyuumi.dev@gmail.com>

Co-authored-by: Yuki Okushi <huyuumi.dev@gmail.com>

src/request.rs

@@ -206,8 +206,14 @@ impl HttpRequest {
         &self.0.config
     }
 
-    /// Get an application data stored with `App::extension()` method during
-    /// application configuration.
+    /// Get an application data object stored with `App::data` or `App::app_data`
+    /// methods during application configuration.
+    ///
+    /// If `App::data` was used to store object, use `Data<T>`:
+    ///
+    /// ```rust,ignore
+    /// let opt_t = req.app_data::<Data<T>>();
+    /// ```
     pub fn app_data<T: 'static>(&self) -> Option<&T> {
         if let Some(st) = self.0.app_data.get::<T>() {
             Some(&st)