add: "ask about this" from neospring

crates/core/src/model/communities.rs

@@ -387,6 +387,9 @@ pub struct QuestionContext {
     /// If the owner is shown as anonymous in the UI.
     #[serde(default)]
     pub mask_owner: bool,
+    /// The POST this question is asking about.
+    #[serde(default)]
+    pub asking_about: Option<usize>,
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize)]