p-multiSelect disabled option still possible to select

[leonardolessa]

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Plunkr Case (Bug Reports)
I've tried to use the issue template but for some reason it was giving me error that options was not an attribute of p-multiSelect.

Current behavior
the SelectItem api has an option to disable (disabled property) but in the multiselect component is just visually disabled, but you can still click in the checkbox and change its selection.

Expected behavior
Block the option so it's not possible to select or "unselect".

Minimal reproduction of the problem with instructions
Just create an multiselect and disable one of the options, you can still change its value although its visually disabled.

[leonardolessa]

Thanks @cagataycivici