feat: toggle formatting of selected area instead of double-wrapping

enhance: select formatted text after changing its formatting for toggle support
fix: place cursor between (pattern)(pattern) pair when selection is empty

src/main/frontend/util/cursor.cljs

@@ -58,6 +58,9 @@
        (= (count (.-value input))
           (.-selectionStart input))))
 
+(defn set-selection-to [input n m]
+  (.setSelectionRange input n m))
+
 (defn move-cursor-to [input n]
   (.setSelectionRange input n n))