Add justify option in export

[virgile-dev]

Feature Request

Is your feature request related to a problem or unsupported use case? Please describe.
As a user, I want to be able to justify my text.

Describe the solution you'd like
Add the option on the editor.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Discovery, Documentation, Adoption, Migration Strategy
The justify option is supposed to be native in BlocNote.js : https://www.blocknotejs.org/docs/editor-basics/default-schema#default-block-properties

This is especially important for users who want to export the doc.

Pointers by Yousef (blocnote.js)
https://github.com/numerique-gouv/impress/blob/50891afd055b5dada1d34e57ab447638865410af/src/frontend/apps/impress/src/features/docs/doc-editor/components/BlockNoteToolbar.tsx#L17

-> this is where you add the formatting toolbar buttons. By default, they don't include a button for "justify", so you'd have to add that yourself
e.g.: <TextAlignButton textAlignment={"justify"} key={"textAlignJustifyButton"} />,

[virgile-dev]

Hey @AntoLC Pierre P. asked for this multiple times. Could we ship this before the end of the month ?

[virgile-dev]

@rl-83 would love to get your thoughts about this.
For the record the users that asked for this don't want to justify while editing in the web but when they export a document.

[rl-83]

I am not in favor of adding justification in the editing process. For me, it goes against the philosophy of Docs, which aims to abstract from layout to simplify the writing experience. It is scientifically recognized that the inconsistency of spacing in justified text makes it less readable and, therefore, less accessible than left-aligned text. This means that if we add justification in the editing stage, we are deliberately hindering the effectiveness of users.

On the other hand, I support adding justification as an export option, as this does not compromise the production efficiency of the document. Here is my proposal (Figma):