Feat: Add system notification for updates

[AmaLuci]

When a new update is available I would like to display a system notification with the information in addition to the notification dot we display in the about section (which may go unnoticed). The same behavior should be applied to all platforms (Mac, Windows, Linux)

Changes Move update link from https://nethesis.github.io/nethlink/ to https://nethserver.github.io/nethlink/

Behavior On click open the download page in the browser.

Content Title: Update available Description: Click to open the download page

Notification dot color and behavior A pulsing "red dot" appears pulsing for few seconds. The color that used to be Primary (on calls for a missing call, on about for updates) must be changed in red:

• Dark theme: red-500
• Light theme: red-700 See Ping animation.

[therockerline]

Unfortunately, the onclick event of the notification system does not work in Electron, so this function is not available until electron solves the problem of onclick behaviour.

[edospadoni]

Test case 1 (mandatory on Windows & Mac, optional on Linux):

• open an older NethLink version
• check the About section (with i icon) is pulsing
• click on the About section
• check if icon stops pulsing

Test case 2 (mandatory on Windows & Mac, optional on Linux):

• open current NethLink version
• check the About section (with i icon) is not pulsing

Testing release: https://github.com/NethServer/nethlink/pull/36#issuecomment-2444424782