1. Previously, the label and tooltip for all recommendations was just "Recommendation", even though the icon was different for extension and feature recommendations.
Because users might not be able to see the icon and/or determine its meaning, it is important that this is communicated in the tooltip and a11y label.
2. Screen reader users won't know this has appeared, even though this attracts some attention visually.
Therefore, provide a specific announcement for screen reader users when the recommendation appears.
Differential Revision: https://phabricator.services.mozilla.com/D47718
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