Description

The limel-chip component already supports an invalid prop that visualises
a chip in an error state (red background with a chessboard pattern, white text).
However, when chips are rendered via limel-chip-set, consumers can only mark
the chip-set as a whole as invalid — there is no way to flag specific entries
in the value array as invalid.

Motivation

A common use case is an input chip-set of free-form values (such as email
addresses or tags) where some individual entries may fail validation while
others are valid. Today, consumers have to either:

• show a single container-level error (useless when most entries are valid), or
• swap the chip icon and hope that communicates the problem.

Neither gives a proper per-chip visual error state, even though limel-chip
itself already supports it.

Proposed solution

Add an optional invalid field to the Chip interface and forward it through
limel-chip-set to the rendered limel-chip, so consumers can flag
individual chips as invalid via the value array:

value = [
  { id: 1, text: 'alice@example.com' },
  { id: 2, text: 'not-an-email', invalid: true, icon: 'error' },
  { id: 3, text: 'bob@example.com' },
];

This is independent of the existing chip-set-level invalid prop, which
continues to mark the whole field as invalid.