quill_delta library Null safety

TODO: Remove this file in the next breaking release, because implementation files should be located in the src folder, https://bit.ly/3fA23Yz.

Classes

Delta
Delta represents a document or a modification of a document as a sequence of insert, delete and retain operations. [...]
DeltaIterator
Specialized iterator for Deltas.
Operation
Operation performed on a rich-text document.

Typedefs

DataDecoder = Object? Function(Object data)
Decoder function to convert raw data object into a user-defined data type. [...]