Refactor & style AnnouncementBox

[andycochran]

• Moves the AnnouncementBox component to the site header so it's available on all routes
• Uses Ember Tooltips instead of custom action to toggle the announcement (added benefit of clicking anywhere on page to close it)
• Adds what-input to prevent :focus outline styles showing for non-keyboard navigation
• Adds some temporary overrides for Labs UI and Ember Tooltips (should be remove once this PR has been merged/published)
• Updates the language of the announcement to be more friendly/positive

[allthesignals]

We should make sure that what-input doesn't break fastboot pre-rendering. Because that happens Node-side, we can't always expect there to be a window object.

[allthesignals]

Looks great! Why keep this inside the component instead of passing it as a block from the invoking side?

[andycochran]

That would work. I had the whole thing in the site header, without using a component at all. I hastily moved it into the component. Makes sense to use it as a block component with the content in the header.

[allthesignals]

@andycochran

Adds what-input to prevent :focus outline styles showing for non-keyboard navigation

Can we address this in a separate issue?

[andycochran]

The reason I added what-input into this PR instead of addressing separately is because the new item in the site menu is a <button> element (the others are <a>) and when you click it you get the focus style.

You can notice the focus style on other elements too (like the dropdown in the BBL Lookup).