Enhancement: Word Editor - Second Iteration Features

The current word editor is basic and lacks important features for user convenience and responsiveness. Enhancements are needed to improve the user experience and usability of the editor and we wish to do this incrementally.

This PR https://github.com/jargonsdev/jargons.dev/pull/6 implemented the `First Iteration`

#### Proposed Features for Second Iteration:
1. **Window Resizer:** Add functionality to resize the side-by-side Editor and Preview panes, allowing users to adjust the size according to their preference.
2. **Mobile Responsiveness:** Ensure that the markdown editor is responsive on mobile devices, providing a seamless experience for users on different screen sizes.
3. **UI Toggle:** Implement a toggle for the Editor and Preview panes, allowing users to display one or both panes on the screen at the same time.

#### Implementation Details:
- **Window Resizer:** Use JavaScript (preferably packed within a custom hook to be consumed inside of the `word-editor` island) to implement a draggable handle that adjusts the width of the Editor and Preview panes dynamically.
- **Mobile Responsiveness:** Use CSS media queries to adjust the layout and styling of the editor for different screen sizes, ensuring readability and usability on mobile devices.
- **UI Toggle:** Implement a button or control that allows users to show/hide the Editor and Preview panes independently or together.

#### Acceptance Criteria:
- Users can resize the Editor and Preview panes by dragging a handle between them.
- The word editor is responsive and displays correctly on mobile devices.
- Users can toggle the visibility of the Editor and Preview panes individually or together.

#### Related Tasks:
- Implement the window resizer functionality using JavaScript.
- Apply CSS media queries to make the editor mobile responsive.
- Implement the UI toggle functionality for showing/hiding panes.

#### Additional Notes:
- This second iteration will significantly improve the usability and flexibility of the word editor, enhancing the overall user experience.

Start at the existing word-editor island and review the First Iteration implementation in PR #6. Break the work into the resizable panes, mobile layout, and editor/preview visibility controls, then verify each acceptance criterion across desktop and mobile screen sizes.

Written by the indexing model from the issue text.