feat: add code autocomplete with Ctrl+Space

[Somoru]

Adds autocomplete functionality using CodeMirror's show-hint addon. Press Ctrl+Space to show word suggestions from the current document.

Closes #2567

Description

This PR implements code autocomplete functionality for the editor using CodeMirror's built-in show-hint addon. Users can now press Ctrl+Space to see a dropdown of word suggestions based on the current document content.

Changes made:

• Added Ctrl+Space keybinding in CodeEditor.js
• Loaded show-hint and anyword-hint addons in HTML files
• Works with all content types: code snippets, PlantUML, markdown

How it works:

• User presses Ctrl+Space while typing
• Autocomplete dropdown appears with matching words from the document
• Navigate with arrow keys, select with Enter/Tab, dismiss with Esc

Issue fixed

Closes #2567 - Adds automatic code completion like vim for writing snippets and PlantUML

Type of changes

• ⚪ Bug fix (Change that fixed an issue)
• ⚪ Breaking change (Change that can cause existing functionality to change)
• ⚪ Improvement (Change that improves the code. Maybe performance or development improvement)
• 🔘 Feature (Change that adds new functionality)
• ⚪ Documentation change (Change that modifies documentation. Maybe typo fixes)

Checklist:

• 🔘 My code follows the project code style
• ⚪ I have written test for my code and it has been tested
• 🔘 All existing tests have been passed
• ⚪ I have attached a screenshot/video to visualize my change if possible
• 🔘 This PR will modify the UI or affects the UX
• 🔘 This PR will add/update/delete a keybinding

---

IssueHunt Summary

Referenced issues

This pull request has been submitted to:

• #2567: code auto complete

---