Add paste button for token in advanced mode [Proper PR]

[robigan]

Adds the ability to paste the token from the clipboard once redirected to the Winston callback URI when trying to add tokens in advanced mode. I had a couple problems with the safari extension working unexpectedly and this helped with development where app links couldn't be used (for some reason or another, not sure). Additionally, if one needs to copy the token from another device, this simplifies it. Either way, I think it would be a nice addition to have as a fallback.

LMK if I should add some screenshots

P.S. I accidentally created the wrong PR in #537 merging into base. Hence my new PR into alpha.