Allow custom roles for chip groups and chips

[ienzam]

Please describe the feature you would like to request.

MatChipList and MatChip do not support providing role attribute. Add support for that.

What is the use-case or motivation for this proposal?

I want to use MatChipList and MatChip as radiobox and radio respectively for better accessibility support. But can't override.

Is there anything else we should know?

Should be a trivial change. I can send a PR.

[ienzam]

Current hack I am using:

/** Hack to override role of MatChipList which is not supported natively. */
@Directive({selector: 'mat-chip-list[role]'})
export class MatChipListRoleOverride {
  @Input() @HostBinding('attr.role') role?: string|null;
}

/** Hack to override role of MatChip which is not supported natively. */
@Directive({selector: 'gmat-suggestive-chip[role]'})
export class MatChipRoleOverride {
  @Input() @HostBinding('attr.role') role?: string|null;
}