Improvements to gov banner

[maxatdetroit]

A few improvement requests:

• The down chevron should rotate 180 degrees when the dropdown opens/closes to indicate the link now closes/opens the dropdown
• The display of the content container should use an ease-in-out animation instead of abruptly appearing
• The info section should be have a part attribute enabling it to be styled from the light DOM. Specifically, I should be able to override the left and right margins of the content so that the edges line up with the main content of the site where the banner is used.

Example of how I found these issues when using the component on a real site:

Screen.Recording.2025-04-10.161648.mp4

[maxatdetroit]

FYI @sreidthomas I assigned this to you but this is lower priority than both the profile component and the detroitatwork banners.