emit "DC_EVENT_MEMBER_ADDED" and python plugin event "member_added" for securejoin or non-securejoin additions of a contact to a chat. also fixup some docs

src/chat.rs

@@ -1958,6 +1958,10 @@ pub(crate) fn add_contact_to_chat_ex(
             chat_id,
             msg_id: msg.id,
         });
+        context.call_cb(Event::MemberAdded {
+            chat_id,
+            contact_id: contact.id,
+        });
     }
     context.call_cb(Event::MsgsChanged {
         chat_id,

src/events.rs

@@ -207,4 +207,10 @@ pub enum Event {
     /// @param data2 (int) contact_id
     #[strum(props(id = "2062"))]
     SecurejoinMemberAdded { chat_id: ChatId, contact_id: u32 },
+
+    /// This event is sent for each contact added to a chat.
+    /// @param data1 (int) chat_id
+    /// @param data2 (int) contact_id
+    #[strum(props(id = "2063"))]
+    MemberAdded { chat_id: ChatId, contact_id: u32 },
 }

src/securejoin.rs

@@ -750,7 +750,7 @@ pub(crate) fn handle_securejoin_handshake(
                             group: field_grpid.to_string(),
                         }
                     })?;
-                context.call_cb(Event::SecurejoinMemberAdded {
+                context.call_cb(Event::MemberAdded {
                     chat_id: group_chat_id,
                     contact_id,
                 });