Customize the behavior of merging format values

[Rain-Zheng]

We are working on a feature that displays a prompt in the formatting bar when the selected content contains multiple formatting values. For example, if the selected content includes text elements with both "Aptos" and "Arial" fonts, a "Multiple fonts" prompt will be shown to the user. So we are adding a parameter to getFormatState to allow customization of the merge behavior.

[JiuqingSong]

Instead of providing a callback, I prefer to add a parameter to indicate how to solve conflict format, and default value is to "remove" (current behavior)

For example:

type ConflictFormatSolution = 'remove' | 'keepFirst' | 'returnMultiple';

export function getFormatState(editor: IEditor, conflictSolution: ConflictFormatSolution = 'remove') {
 ...
}