Handle configuration changes without needing to restart

[jiribenes]

Something like the following should work:

    context.subscriptions.push(vscode.workspace.onDidChangeConfiguration(e => {
        if (e.affectsConfiguration('effekt')) {
            const newConfig = vscode.workspace.getConfiguration('effekt');
            handleConfigChange(newConfig, client);
        }
    }));

The easiest thing is to probably restart the LSP server, just be careful to do it correctly :)