feat: Implement basic general folder support (#2051)

- Related: #1748

tests/ha/supports-feature.test.ts

@@ -0,0 +1,41 @@
+import { describe, expect, it } from 'vitest';
+import { supportsFeature } from '../../src/ha/supports-feature';
+import { createStateEntity } from '../test-utils';
+
+describe('supportsFeature', () => {
+  it('returns true if the feature bit is set', () => {
+    const stateObj = createStateEntity({
+      attributes: { supported_features: 4 },
+    });
+    expect(supportsFeature(stateObj, 4)).toBe(true);
+  });
+
+  it('returns false if the feature bit is not set', () => {
+    const stateObj = createStateEntity({
+      attributes: { supported_features: 2 },
+    });
+    expect(supportsFeature(stateObj, 4)).toBe(false);
+  });
+
+  it('returns false if supported_features is undefined', () => {
+    const stateObj = createStateEntity({
+      attributes: {},
+    });
+    expect(supportsFeature(stateObj, 1)).toBe(false);
+  });
+
+  it('returns true if multiple feature bits are set and one matches', () => {
+    const stateObj = createStateEntity({
+      attributes: { supported_features: 6 }, // 2 + 4
+    });
+    expect(supportsFeature(stateObj, 2)).toBe(true);
+    expect(supportsFeature(stateObj, 4)).toBe(true);
+  });
+
+  it('returns false if feature is 0', () => {
+    const stateObj = createStateEntity({
+      attributes: { supported_features: 7 },
+    });
+    expect(supportsFeature(stateObj, 0)).toBe(false);
+  });
+});