DBNotification: set default roles

[d-koppenhagen]

The DBNotification component should have default HTML role attributes based on their semantic purpose to enhance accessibility.
By assigning appropriate role attributes to elements inside the DBNotification component, we can improve how assistive technologies interact with these notifications.
Below are some suggestions for HTML role attributes for different parts of the component:

The resulting <article class="db-notification"> element should have appropriate semantic roles based on the data-semantic attribute. Notifications with critical, warning, or informational semantics could use roles like alert, status, or log respectively.

Relevant Links:

• Web Accessibility Initiative (WAI) guidelines: WAI Roles and Properties