Add warning about IntelliSense to PSIC terminate dialog (#3976)

This came up in a user group that many people weren't aware of, so I think enhancing this message is appropriate.

Co-authored-by: Andy Schwartzmeyer <[email protected]>

Author: JustinGrote

src/session.ts

@@ -508,7 +508,7 @@ export class SessionManager implements Middleware {
 
     private promptForRestart() {
         vscode.window.showErrorMessage(
-            "The PowerShell session has terminated due to an error, would you like to restart it?",
+            "The PowerShell session has terminated due to an error, would you like to restart it? (IntelliSense will not work unless the PSIC is active and unblocked.)",
             "Yes", "No")
             .then((answer) => { if (answer === "Yes") { this.restartSession(); }});
     }