fix(runtime-core): warn about negative number in v-for

[cyrilf]

Context

When using v-for with a negative value, let's say -1, an error occurs in the console:

RangeError: Invalid array length

You can see a reproduction here.

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Proposed solution

If the number wasn't an integer, we would get a nice warning:

I'm just extending this warning to also includes negative integers.
This way, it's way easier to understand that the issue arises in the v-for and goes into debugging the issue faster.

You can see a reproduction of the fix live here. (the console is correctly warning [Vue warn]: The v-for range expects a positive integer value but got -1. )

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Side note

• I did a commit for the server-renderer, to stay aligned with the runtime-core change.
  This one was failing silently as it's using a for loop compared to the runtime-core using a new Array(source) where source was -1, hence resulting in the RangeError: Invalid array length error message.

• I did a second commit for the runtime-core package, the one I want to fix.

(actually this issue arised from using the carousel from NuxtUI, but I see that the page / indicators calculation has now been fixed but I still think that this fix is nice to have)