Add extra warning about using brace initialization on json when we shouldn't.

Changes.txt

@@ -14,6 +14,12 @@
 
 6.6 to 6.7 (June 6, 2022)
 
+  * IMPORTANT NOTES:
+    - Because of fixes to JSON handling, all remappings will be reset
+      to defaults; if you had custom mappings, they will need to be
+      re-entered again.
+    - Because of internal changes, all state files are now invalid.
+
   * Completely reworked the file launcher:
     - Redesigned user interface
     - Added tracking of user favorites, recently played and most popular

src/common/PJoystickHandler.hxx

@@ -49,6 +49,10 @@ class PhysicalJoystickHandler
   private:
     struct StickInfo
     {
+      // NOTE: For all future linting exercises
+      //       Make sure to *NEVER* use brace initialization or std::move
+      //       on the 'mapping' instance variable; there lay dragons ...
+      // https://json.nlohmann.me/home/faq/#brace-initialization-yields-arrays
       explicit StickInfo(nlohmann::json map, PhysicalJoystickPtr stick = nullptr)
         : mapping(map), joy{std::move(stick)} {}