Introduce error message prop

[geoffrich]

Is your feature request related to a problem? Please describe.

auro-select supports an error state with a red border, but does not support displaying an error message. In my application I need to show an error associated with a select, e.g. "Please select an option"

Describe the solution you'd like

Introduce a prop so that an error message can be displayed.

Describe alternatives you've considered

Handle showing the error message in my application code, e.g.

<auro-select error={showError}>
    <!-- truncated for readability -->
</auro-select>
{#if showError}
    <p class="errorText">{error}</p>
{/if}

Though this solution is not properly associated with the select using aria-describedby. An solution inside the component would make that easier.

Additional context

Prior art in auro-input:

[blackfalcon]

@leeejune I am not finding the error state for this element in the blueprints? https://www.figma.com/file/nyXRAgG4YzZaGdIVmPwARP/Select?node-id=322%3A298

Is this defined?

[blackfalcon]

Not sure yet to define this as a bug or a new feature.

[leeejune]

Since it uses input, I didn't display the other states; I assumed that it would inherit all of input's states... should I display all of the states?

[blackfalcon]

Closing issue in favor of new feature work

• Update feature to use new validity pattern #118