`just --fmt` should preserve single-value attribute syntax

Summary

Please consider adding a formatter option that controls how single-value attributes are rendered by just --fmt.

At present, just --fmt unconditionally converts colon-separated single-value attributes to the function-style syntax. For example:

[doc: "doc"]
[group: "group"]

is formatted as:

[doc("doc")]
[group("group")]

Proposed behavior

A formatter option could allow users to select the preferred syntax for single-value attributes. For example, users could choose between:

[doc: "doc"]

and:

[doc("doc")]

The exact option name and syntax are open for discussion. Possible approaches include a command-line option, a configuration setting, or a formatter-specific setting in the justfile.