fix(shortcut): job shortcut only run when have job

The shortcut was always allowed to run, meaning when the player doesn't
have a job, they were sent to the job screen with no job and lost the
view context/sidebar.

- Add utility method to check if the player 'hasJob', being at least 1
job.
- Check if player has job when the key combination is pressed

Resolves danielyxie/bitburner#2013

src/PersonObjects/IPlayer.ts

@@ -242,6 +242,7 @@ export interface IPlayer {
   getIntelligenceBonus(weight: number): number;
   getCasinoWinnings(): number;
   quitJob(company: string): void;
+  hasJob(): boolean;
   createHacknetServer(): HacknetServer;
   startCreateProgramWork(router: IRouter, programName: string, time: number, reqLevel: number): void;
   queueAugmentation(augmentationName: string): void;