Adding detect key events and fixing back space issue

The backspace update from editor-js#95 worked, but the event listeners
are lost when the toggleTune is invoked. This
PR adds the listeners back after the tune is invoked.

The listeners are lost because replaceWith does not
propogate the existing listeners to the new element.

src/index.js

@@ -124,21 +124,7 @@ export default class List {
       this._elements.wrapper.appendChild(this._make('li', this.CSS.item));
     }
 
-    if (!this.readOnly) {
-      // detect keydown on the last item to escape List
-      this._elements.wrapper.addEventListener('keydown', (event) => {
-        const [ENTER, BACKSPACE] = [13, 8]; // key codes
-
-        switch (event.keyCode) {
-          case ENTER:
-            this.getOutofList(event);
-            break;
-          case BACKSPACE:
-            this.backspace(event);
-            break;
-        }
-      }, false);
-    }
+    this.detectKeyEvents()
 
     return this._elements.wrapper;
   }
@@ -207,7 +193,10 @@ export default class List {
       ...item,
       isActive: this._data.style === item.name,
       closeOnActivate: true,
-      onActivate: () => this.toggleTune(item.name)
+      onActivate: () => {
+        this.toggleTune(item.name)
+        this.detectKeyEvents()
+      }
     }))
   }
 
@@ -360,6 +349,29 @@ export default class List {
     return currentNode.closest(`.${this.CSS.item}`);
   }
 
+
+  /**
+   * Add keydown listeners for escaping from a list and 
+   * back space events.
+   */
+  detectKeyEvents() {
+    if (!this.readOnly) {
+      // detect keydown on the last item to escape List
+      this._elements.wrapper.addEventListener('keydown', (event) => {
+        const [ENTER, BACKSPACE] = [13, 8]; // key codes
+
+        switch (event.keyCode) {
+          case ENTER:
+            this.getOutofList(event);
+            break;
+          case BACKSPACE:
+            this.backspace(event);
+            break;
+        }
+      }, false);
+    }
+  }
+
   /**
    * Get out from List Tool
    * by Enter on the empty last item
@@ -397,7 +409,14 @@ export default class List {
    */
   backspace(event) {
     const items = this._elements.wrapper.querySelectorAll('.' + this.CSS.item),
-        firstItem = items[0];
+      firstItem = items[0];
+
+    if (this.currentItem.textContent.trim() === '') {
+      const target = this.currentItem;
+      window.requestIdleCallback(() => {
+        target.parentElement.removeChild(target);
+      })
+    }
 
     if (!firstItem) {
       return;