Improve compatibility between server and client

[NiklasRentzCAU]

If the server or client has an API-breaking change and both KLighD and klighd-vscode are released, VS Code will automatically update the klighd-vscode version, whereas the server needs to be updated to the latest KLighD version manually, thus possibly leading to working installations in VS Code to suddenly break without notice. A current workaround is to manually force to use an old klighd-vscode release instead.

A solution to this problem is that the server should always notify klighd-vscode about its version in the init message so that klighd-vscode can warn the user about an incompatible version and possibly also disable new features related to that new release unless the server version is compatible.
Special case to note: If the server does not provide a version number (as of the current release), set it accordingly on the client.