Update webapp example

[ramsayleung]

Description

Features:

• Add token refreshing
• Use the new API properly (at some point we do spotify.token = ..., we can surely avoid that).
• Proper error handling? It has too many unwrap in my opinion.
• Add string interpolation where possible
• Include it in the CI somehow so that this doesn't happen anymore.

Motivation and Context

#324

Dependencies

• log
• env_log
• cookie

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How has this been tested?

Is this change properly documented?

Not yet.

[marioortizmanero]

Thanks for the contribution and sorry for the late PR! Can confirm that this works wonderfully and fixes #324. We should first merge #374 so that CI passes all the checks.