feat(richtext-lexical)!: add FixedToolbarFeature

[AlessioGr]

Description

BREAKING:

• The default inline toolbar has now been extracted into an InlineToolbarFeature. While it's part of the defaultFeatures, you might have to add it to your editor features if you are not including the defaultFeatures and still want to keep the inline toolbar (floating toolbar)

• [ ] I have read and understand the CONTRIBUTING.md document in this repository.

Type of change

• [ ] Chore (non-breaking change which does not add functionality)
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Change to the templates directory (does not affect core functionality)
• [ ] Change to the examples directory (does not affect core functionality)
• [ ] This change requires a documentation update

Checklist:

• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] Existing test suite passes locally with my changes
• [ ] I have made corresponding changes to the documentation