Description

This PR migrates the Rich Text editor from Slate to Lexical used in Payload. While both Slate and Lexical save the editor state in JSON, the structure of the JSON is different, thus requiring a migration to convert all previously saved Rich Text content to the new format.

Fixes #1120

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Screenshots

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation