Feat: support for customize `onKey` events

[CatHood0]

Description

[!NOTE] This PR has been moved to #2368.

A new parameter was added with the name onKeyPressed, which as its name indicates, calls this function every time a key on the keyboard is pressed.

Why was this done?

This is because previously the user never had the opportunity to prevent a key from executing its default function, because we handled all this internally.

It was decided to pass two parameters in this function, the KeyEvent and a Node that corresponds to the current node that is in selection.

Example

If we want to prevent all Embed Objects from being deleted, we would only have to create a function such that:

QuillEditor(
  controller: _controller,
  config: QuillEditorConfig(
     onKeyPressed: (event, node) {
       if (event.logicalKey == LogicalKeyboardKey.backspace && (node is Line || node is Block)) {
          final iterator = DeltaIterator(_controller.document.toDelta())
               ..skip(_controller.selection.baseOffset - 1);
          final cur = iterator.next();
          if (cur.data is! String && cur.data != null) {
             return KeyEventResult.handled;
          }
       }
       return null;
     },
  ),
)

Related Issues

• Fix #2308

• [x] ✨ New feature: Adds new functionality without breaking existing features.

• [ ] 🛠️ Bug fix: Resolves an issue without altering current behavior.

• [ ] 🧹 Code refactor: Code restructuring that does not affect behavior.

• [ ] ❌ Breaking change: Alters existing functionality and requires updates.

• [ ] 🧪 Tests: Adds new tests or modifies existing tests.

• [ ] 📝 Documentation: Updates or additions to documentation.

• [ ] 🗑️ Chore: Routine tasks, or maintenance.

• [ ] ✅ Build configuration change: Changes to build or deploy processes.

[EchoEllet]

I will solve the conflicts of this PR and the others soon.

[EchoEllet]

Closing this PR since I don't have permission to push to the fork or merge changes to the master branch of this repo while fixing the conflicts. Submitted a new PR (#2368).