fix(Inertia): target blank flag links as external

[Barbapapazes]

Note

For v4 branch, see #4746 for v3

Hello 👋,

This PR fixes a bug where the following button:

<template>
  <UButton
    href="/admin"
    target="_blank"
  />
</template>

triggers an Inertia request, opening the link in an Inertia modal instead of a new tab.

This happens because a blank target is not treated as an external link, and Inertia ignores the target prop. As a result, Inertia fetches the URL, returns HTML, and displays it in the modal.

[benjamincanac]

Closing this as v4 branch follows v3, everything from v3 is rebased into v4!