Koenig - Ensure Enter behaviour is consistent when a card is selected

refs TryGhost/Ghost#9623
- clicking a card a second time while it is selected can move the invisible cursor to the beginning of a section in which case <kbd>Enter</kbd> would insert a blank paragraph above the card
- when <kbd>Enter</kbd> is pressed and a card is selected, move the cursor to the end of the card section without triggering our cursor change so that the default behaviour will always add a paragraph after the card

lib/koenig-editor/addon/options/key-commands.js

@@ -33,6 +33,12 @@ export const DEFAULT_KEY_COMMANDS = [{
             return;
         }
 
+        // if a card is selected, move the cursor to the end of the card so that
+        // Enter consistently adds a new paragraph after the card
+        if (isCollapsed && section.isCardSection) {
+            koenig.moveCaretToTailOfSection(section, true);
+        }
+
         return false;
     }
 }, {