Changes:

• Fixes #52
• Improved caching logic around failed requests. Caches failed responses for 1 day to reduce server load on ProtonDB and Steam, making it faster to run after stopping a long-running check. In my testing, this reduced a 9000+ game library from over an hour to just a couple of minutes.
• Adds a 3 second timeout to all requests, since by default there is no timeout for requests the script would wait indefinitely for a response that would never come. The exact timeout period may change in the future, this seemed like a good value to me for now though.
• Add a time taken output at the end of the script to give some more info to the user. This should make it easier to spot when regressions that make it take longer happen as well.
• Add a user agent to the script to allow ProtonDB and Steam to measure the traffic that is generated on their servers by this script.