Add style warning for `[id]`

[JoaoFelipe3]

This is a minor enhancement, but please add a style warning for [id], telling the user to replace it with fix. You could also add a warning for {id} and [box], telling the user to replace those with fixbox, or for the matter, any function with a single output (multiple functions too) wrapped in braces, replacing the braces with fix.

[kaikalii]

I'll have to think about this.
I think there may be some cases where [∘] is valuable for clarity or intent.
fix ¤ is mostly about "fixing" an array for use in a loop, while [∘] conveys the creation of a singleton list.

[JoaoFelipe3]

It might only be me, but I like fix more, because it's a single glyph, and for me, any kind of parenthesis or bracket is a little off-putting. 🫤