svelte5: Better error message for binding to undefined variables

[ottomated]

Describe the problem

The current error message for attempting to bind to an undefined variable is Can only bind to state or props, which is technically correct but confusing. REPL

Describe the proposed solution

The error message here should be something like Cannot find name 'x'..

Importance

nice to have

[rChaoz]

Should probably copy the error message from non-bindings - x is not defined

[dummdidumm]

In a sense it's correct, this is a global variable, so not state nor props

[ottomated]

Yes, as I said it's technically correct, but the most common place people will run into this is A. misspelling a local state or B. renaming / deleting local state without updating the binding. The error could have a disclaimer about global variables if you think it needs that, but it's such an edge case.
i.e.

x is not defined.
If x is a global variable, bind using globalThis.x

or

x is not defined.
You can only bind to existing local state and props