Make the homepage more informative

[MihanEntalpo]

The main page "/" - make it informative so that the newcomer does not get confused.

For those who have already used the system, immediately give the main buttons - Go to clipboard, Share key, Add key

For those who haven't used it yet, show quick, super-simple user manual.

1. The main function is to show the addition via QR code and anonymity
2. Additional features - pass key by reference

It would be great to make a video and post it on youtube. In general, entire home page can be made as a landing page, where all the functionality is summarized.