Config option to set formatter tab width

[AgentElement]

Motivation

typstyle v0.12.15 now has support for a --tab-width flag. I think that a user should be able to configure tinymist to set a value for this flag in their editor config.

Description

Add a new formatterTabWidth option to init::CONFIG_ITEMS. Pass the value directly to typstyle with the new .with_tab_spaces() method.

Notes
This feature will not be available for users of typstfmt. I do not think this is an issue, as typstfmt is archived and no longer accepts PRs.

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Would this feature be appreciated? I intend to work on it, and it is a relatively small change.