chore!: move spell checker to example

[EchoEllet]

Description

Remove simple_spell_checker from flutter_quill_extensions to make it optional in order to reduce bundle size. Implementing this feature in the example.

This PR will not require any additional changes to build the app however it will disable the spell-checking feature.

Initially, I planned on moving this feature into a new package (flutter_quill_spell_checker) and while doing so, I decided to only implement it in the example for a few reasons.

The README.md has been updated.

Apologies for the frequent breaking changes; we're continuously refining decisions to improve the project's direction.

Tip

For existing apps that expect this feature, you can take a look at the example and Spelling checker page.

Open to feedback—feel free to ask any questions or share thoughts.

Related Issues

• Fix Make spell checker package optional #2142
• Related Chore: improve Spell checker API to the example #2133
• Related Feat: Spellchecker for Flutter Quill #2118
• Related Should we add a spellchecker for Editor? #2108

Type of Change

• ✨ 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.

Suggestions

I recommend that we focus on code quality by refactoring and enhancing the existing code, documenting it, making it more extensible by allowing to write extensions to provide any feature in a clean way, and more tests since we have regressions more often than before.

[CatHood0]

For now I'm fine with these changes, however, I think it's important to point out in the project's README that having this feature could increase the bundle size.

Thanks for taking the time to make these changes.

As you mentioned, it's best to focus for now on the existing code that still causes some issues (some I haven't been able to find the solution for).