Simplify github token registration process

[praveen-kanamarlapudi]

What feature are your requesting?
Simplify github token registration process

What benefits do you foresee from the feature you are requesting?
Simplifies user experience and multiple hooks in the using the extension.

Potential solution/ideas?

1. Create a register github token button in notebooks UI.
2. Ask for user credentials on clicking the button.
3. Authenticate with github and store the token securely and reuse.

Additional context