feat: add MLFQ scheduling algorithm and thread scheduler

- Implemented MLFQ (Multilevel Feedback Queue) algorithm with dynamic priority levels and quantum management.
- Created unit tests for MLFQ algorithm covering initialization, demotion, selection, priority boost, preemption, and quantum expiration.
- Developed a ThreadScheduler class supporting FCFS, RR, and PRIORITY scheduling policies for intra-process thread management.
- Added unit tests for ThreadScheduler to validate thread selection and quantum expiration logic.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "pss",
-  "version": "1.2.0",
+  "version": "1.3.0",
   "description": "Process Scheduler Simulator — an interactive educational tool that runs entirely in the browser",
   "main": "index.js",
   "scripts": {