[A11Y] amp-list, list role should be on the container not the element

[aghassemi]

The role=list should be on the container_ which is the parent of role=listitem children. Currently the role is on the element itself and TalkBack is not announcing items as list items. Alternative approach is using aria-owns but that's not worth it.

Also we should fix the examples on https://ampbyexample.com/components/amp-list/ they are invalid HTML and there is no need for the wrapper UL and LI children.

They should just be

    <amp-list width=auto
        height=100
        layout=fixed-height
        src="https://ampbyexample.com/json/examples.json">
      <template type="amp-mustache"
          id="amp-template-id">
        <div>
          <a href={{url}}>{{title}}</a>
        </div>
      </template>
    </amp-list>

We should add some text to the example that ensures the author we are using proper aria attributes to make these a list.

If we really like to allow folks to use 'li' as children, then amp-list needs to become smarter and not create the container until it has a child and can inspect the child to see if it is a li or not and based on that either create a div or an ul

[aghassemi]

/to @lannka

[lannka]

hi @kul3r4 do you want to take a look at the ABE issue?

[aghassemi]

Closed by #5740

[lannka]

@aghassemi to track the ABE bug, you might want to open an issue here