Align preference and notification styling with VSCode

[msujew]

What it does

Updates our hovering and focus behavior for preferences and notifications to behave like the current version of VSCode.

How to test

Both of these tests should be performed for different light/dark themes. I changed the color slightly for preferences in the light theme compared to VSCode, since hovering and focus color were completely transparent. In my opinion this didn't really look good.

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1. Open the example app, hover over and click on one of the browser-endpoint notifications.
2. Open the notification center, again, checking hover and click/focus behavior
3. Assert that it aligns to VSCode's behavior

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1. Open the preference widget
2. Hover over different preferences and click on them (focus). The More Actions... gear should only appear when a preference is focused.
3. Change a preference so that it deviates from its original default value. Assert that the appearing vertical bar looks correct.
4. When clicking on a referenced preference, the target preference should be displayed in the center of the widget and should automatically gain the focus.
5. Assert that is aligns to VSCode's behavior

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[colin-grant-work]

Apart from the bug mentioned below, the changes look good. One other thing I noticed is that we currently allow selection of the text of the preference name and description where VSCode does not, but that doesn't have to be addressed here.

[colin-grant-work]

Looks good to me, in various themes. 👍