Memory leak in Shortcuts class

**Editor.js Version**

v2.29.0

**Issue description**

Hi!

I've found a memory leak in the Shortcuts class. When you remove the shortcut for an element you don't check if the element's shortcuts are empty and left the element in the registeredShortcuts map (with an empty array):

https://github.com/codex-team/editor.js/blob/b619946e8f23ebc9ccfc41ef653439278e99491e/src/components/utils/shortcuts.ts#L89

If you create a new EditorJS and destroys it, you will see a bunch of detached elements referenced by registeredShortcuts map.

**Steps to reproduce:**

You can reproduce the issue with this simple html:

```

Remove

let editor = new EditorJS({
holder: 'editor',
});

function remove() {
document.querySelector('#editor').remove();
editor.isReady.then(() => {
editor.destroy();
editor = undefined;
});
}
document.querySelector('#remove').addEventListener('click', remove);

```

Press "Remove" button and take a snapshot in Chrome dev tools. You will see detached HTMLDivElement's referenced by registeredShortcuts:


If you remove the element from the map when the shortcuts array is empty, the problem disappears:

```js
const newShortcuts = shortcuts.filter(el => el !== shortcut);

newShortcuts.length===0?
this.registeredShortcuts.delete(element):
this.registeredShortcuts.set(element, newShortcuts);
```