store and revert to clipboard value before setting it to the OAuth code

**What’s missing?**

When the OAuth Device Flow is triggered, the user's clipboard gets set to the OAuth code for convenience.

The problem is that my Kit script might depend on the previous clipboard, so it would be great if `scriptkit-octokit` would recover the previous clipboard.

**Why?**

I'm writing a script that creates a gist from the current clipboard. When the OAuth device flow is triggered, the created gist contains the OAuth code, not my clipboard :)

**Alternatives you tried**

I'm storing the clipboard before instantiating `scriptkit-octokit`