Coach people in using Shapeshifter when re-copying stuff

[ffMathy]

Related to #245.

If people are copying something again that they already have in their clipboard, we should remind them with a tray icon notification, reminding them that Shapeshifter could have helped.

Shapeshifter is easy to use, but it requires knowing that it's there, which is sometimes hard to get used to since it's so hidden away from everything (which is good).

[thegabrielstein]

Excellent idea! People who haven't been using it for years like I have haha, won't have anywhere close the awareness and mental habits of utilizing it. Great reminder opportunity.

[thegabrielstein]

This vs #245, even if we let users copy twice and just tell them they've copied something twice, and that Shapeshifter is there to help save time from copying stuff over and over and to check the clipboard, that's a great reminder! Not sure if the work needed to deploy a notification like that is the same as solving #245 though haha (so maybe do both instead of just the notification).