Specify Spicetify version in README & check for version in code

[elijaholmos]

Certain features rely on certain Spicetify versions. Include which version(s) are supported by this extension in the README and perform a check when the extension is initializing to ensure it is being used with a compatible Spicetify version.

[elijaholmos]

It would appear that the Spicetify version is not stored anywhere that is accessible by javascript; the only place I can find is in the .go files

[elijaholmos]

This is about as resolved as I can get it at the moment. It's not entirely necessary for the spicetify version to be checked in the extension code, but it'll just make troubleshooting harder on the user's end. Still though, I don't foresee much issues since one of the first things that can be checked in support tickets is the user's currently running version of spicetify.