docs: add JSDoc header to word-editor.jsx (#227)

## Description
This PR adds a JSDoc header to `src/components/islands/word-editor.jsx`.

- Documents the **Word Editor Component System**
- Describes exports: `WordEditor`, `SubmitButton`, `TogglePreview`
- Notes key features: live preview, GitHub integration, responsive
design

This brings consistency with other components such as `word-search.jsx`.

## Related Issue
Closes #217

## Screenshots
Code changes in `word-editor.jsx`:

<img width="2788" height="467" alt="Screenshot of code changes"
src="https://github.com/user-attachments/assets/f388a6b6-d9e1-45e2-bc14-c994d52a2944"
/>

## Notes to Reviewer
No new dependencies added.

Co-authored-by: Olabode Lawal-Shittabey <babblebey@gmail.com>

Author: 1sh-repalto

src/components/islands/word-editor.jsx

@@ -1,3 +1,10 @@
+/**
+ * Word Editor Component System - Dictionary Content Creation & Editing
+ * @exports WordEditor - Main editor with live preview, form validation, and GitHub integration for dictionary contributions
+ * @exports SubmitButton - Detached submit button with loading states and success indicators
+ * @exports TogglePreview - Mobile preview toggle for responsive editor experience
+ */
+
 import { useEffect } from "react";
 import Markdown from "react-markdown";
 import { useStore } from "@nanostores/react";