chore: better ensure script

[manuel3108]

Continuation of this discussion: #858 (comment)
This should be a pretty good intermediate setup. According to AI we could also include that in parseSvelte as a param, as long as we always use a literal directly (true | false) and do not use a variable. That shouldn't be a problem in our case.

But as that part of the code is being touched by #684 already, I don't want to touch the same code here.

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[jycouet]

I like this one a lot