Enhancement: Search within Embed objects

[AtlasAutocode]

Description

Adds the ability to search within custom Embed objects.

For how to enable: refer to documentation, Configurations, Links, Search

https://github.com/singerdmx/flutter-quill/blob/master/doc/configurations/search.md

Related Issues

• Fix Custom content cannot be searched. #2075

Type of Change

• [ X ] ✨ 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.
• [ X ] 🧪 Tests: Adds new tests or modifies existing tests.
• [ X ] 📝 Documentation: Updates or additions to documentation.
• 🗑️ Chore: Routine tasks, or maintenance.
• ✅ Build configuration change: Changes to build or deploy processes.