[UNTNG] Upgrade nudge from macOS to Desktop Electron

This is part of #4285 and is for the work done on the macOS Desktop Classic application

Changes:

• create a popup on app launch with read more and remind me later button
  • read more button opens the url: desktop.github.com/upgrade/classic/ AND reminds the user in 30 days
  • remind me later removes the popup and reminds the user in 30 days
  • clicking on the red traffic light x button removes the popup and reminds the user in 30 days
• final image/copy (see last section in description)
• update copy on About info that no longer says the app is up to date
• provide some steps in the PR on how we can test the reminder popping up in 30 days in code review, given the fact that you are aware of the implementation details

User Flow functionalities to check: (let’s pretend the user is Tracy)

• If Tracy opens the app and somehow quits the app without engaging in the popup (ex: killing the process), they will see the popup appears on the next app launch
• If Tracy resizes the app or connects to an external monitor, the popup appears in the center with a fixed size (500px x 255px) no matter what
• Tracy sees copy that matches macOS casing
• Tracy sees a popup appears after 30 days if they 1) close the popup by x-ing out, 2) clicking on read more, or 3) clicking on remind me later
• If Tracy clicks on read more, it’ll open desktop.github.com/upgrade/classic/ in whatever default browser they have

Other pieces:

• Windows work - #4287
• analytics

Notes:

• img size is 500px x 255px
• you are awesome and thank you

Design

Before

[Before] For popup: Before, Tracy sees Desktop Classic for macOS on app launch

[Before] For about:

After

[After] For popup:

[After] For about:

Image for popup modal

[joshaber]

[agisilaos]

@joshaber Welcome back ❤️