Accessibility on atto

According to an audit made over Accessibility, exist violations over Atto as follows:

• Ensure page tabs contain proper textual descriptions indicating state and role

Affected modules: Submit Assignment

When the "Insert Media" modal is first opened, the "Link" tab is active, however no information is provided to indicate this accessibly. However, once a tab is clicked, the active tab is assigned an aria-expanded attribute of "true".

Steps to locate:
1. Activate the "Media" button in the toolbar next to the "Online Text" text area.
2. Move through the tabs using the tab key. Notice that the screen-reader announces them as having the same state.
3. Activate the "Video" tab. Notice that the screen-reader announces that it has been expanded.
4. Activate "Link." Move through the tabs and notice that "Link" is announced as being expanded.

Ensure that aria-expanded is assigned to the tab control which is active when a modal is first loaded.