Fixed accessibility issues with notification close buttons

[abjerner]

Prerequisites

• I have added steps to test this contribution in the description below

Description

I noticed that the close button icon was a dark color which for most of the notification types were shown on a dark'ish background. The click area for the button was also limited to the width of the icon.

This PR therefore changes the icon color to white (similar to the text color), and makes the icon fully opaque. Since the icon was only 40% opaque in it's default state, the hover effect didn't add any visual effect. Now the icon is 75% opaque on hover, making the effect more visual. IMO the text shadow didn't do anything good, so I've also removed that. While the close button previously had a width of ~12 pixels, it now has a width of 30px, making it easier to hit.

Testing

The following three files make up a dummy dashboard that may be used for testing. The dashboard adds a sticky notification of each type.

/src/Umbraco.Web.UI/App_Plugins/Hello/package.manifest

{
    "$schema": "https://json.schemastore.org/package.manifest",
    "javascript": [
	"/App_Plugins/Hello/Dashboard.js"
    ],
    "dashboards":  [
        {
            "alias": "hello",
            "view":  "/App_Plugins/Hello/Dashboard.html",
            "sections":  [ "content" ],
            "weight": -10
        }
    ]
}

/src/Umbraco.Web.UI/App_Plugins/Hello/Dashboard.js

angular.module("umbraco").controller("Hello.Dashboard", function ($scope, notificationsService) {

  notificationsService.add({
    headline: "Hi",
    sticky: true,
    type: "warning"
  });

  notificationsService.add({
    headline: "Hi",
    sticky: true,
    type: "danger"
  });

  notificationsService.add({
    headline: "Hi",
    sticky: true,
    type: "info"
  });

  notificationsService.add({
    headline: "Hi",
    sticky: true,
    type: "success"
  });

});

/src/Umbraco.Web.UI/App_Plugins/Hello/Dashboard.html

<div ng-controller="Hello.Dashboard as vm">
  Hello there!
</div>

[github-actions]

Hi there @abjerner, thank you for this contribution! 👍

While we wait for one of the Core Collaborators team to have a look at your work, we wanted to let you know about that we have a checklist for some of the things we will consider during review:

• It's clear what problem this is solving, there's a connected issue or a description of what the changes do and how to test them
• The automated tests all pass (see "Checks" tab on this PR)
• The level of security for this contribution is the same or improved
• The level of performance for this contribution is the same or improved
• Avoids creating breaking changes; note that behavioral changes might also be perceived as breaking
• If this is a new feature, Umbraco HQ provided guidance on the implementation beforehand
• 💡 The contribution looks original and the contributor is presumably allowed to share it

Don't worry if you got something wrong. We like to think of a pull request as the start of a conversation, we're happy to provide guidance on improving your contribution.

If you realize that you might want to make some changes then you can do that by adding new commits to the branch you created for this work and pushing new commits. They should then automatically show up as updates to this pull request.

Thanks, from your friendly Umbraco GitHub bot 🤖 🙂

[nathanwoulfe]

Hi @abjerner this looks great - improved UI and improved a11y, it's a double win!