feat: Add testing infrastructure and documentation

- Set up Vitest for unit testing with jsdom
- Add test setup with Web Audio API and requestAnimationFrame mocks
- Create initial test suites for DOM and animations modules
- Add test scripts to package.json (test, test:ui, test:run, coverage)
- Update CI workflow to include test execution
- Create CONTRIBUTING.md with conventional commits guidelines
- Create SECURITY.md with security policy
- Update ESLint config to support test files
- All tests passing (8/8)

Co-authored-by: ZaneThePython <102631678+ZaneThePython@users.noreply.github.com>

tests/animations.test.js

@@ -0,0 +1,40 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest';
+import { typeWriter } from '../assets/js/modules/animations.js';
+
+describe('Animations Module', () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+  });
+
+  describe('typeWriter', () => {
+    it('should type text character by character', async () => {
+      const element = document.createElement('div');
+      document.body.appendChild(element);
+
+      const text = 'Hello';
+      typeWriter(element, text, 50);
+
+      // Wait for first setTimeout to execute
+      await vi.runAllTimersAsync();
+
+      // Complete text should be shown
+      expect(element.innerHTML).toBe('Hello');
+    });
+
+    it('should handle null element gracefully', () => {
+      expect(() => {
+        typeWriter(null, 'text', 50);
+      }).not.toThrow();
+    });
+
+    it('should handle empty text', () => {
+      const element = document.createElement('div');
+      document.body.appendChild(element);
+
+      typeWriter(element, '', 50);
+      vi.advanceTimersByTime(100);
+
+      expect(element.innerHTML).toBe('');
+    });
+  });
+});