Show if no version is available when running tmpo version #24

The feature request

Until we (hopefully) integrate tmpo into an official package manager, it is difficult to know when a new version is available.

Proposed solution

I think when tmpo version is ran, it should show the current version as usual. However, if the user is connected to the internet, it should check to see if a newer version is available. If there is, it should display a message.

Additional context

The only issue I foresee is that this may cause some lag, as it requires a GET request to a server and waits for a response, which could take a second. Because of this, it might be a good idea to perform a check and cache the response in the background whenever a command is run. I'm not sure if this is a good idea or not, but it's definitely worth exploring.