Feat: include spell checker for example app

[CatHood0]

Description

Added the Spell-checker to the sample app which can be turned on or off at the user's discretion.

However, not only this was done but some code parts were added and fixed:

• Added information about the Feature in the README
• Fixed a bug where the editor placeholder is detected as text instead of virtual text which should be ignored
• Updated simple_spell_checker to the latest version to fix issues with state and characters being lost when typing in the editor

Preview:

clideo_editor_41252a306f9b4127809fd227ae4bbdb6.mp4

• ✨ 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.