feat(core): editor setting service (#7956)

define editor setting schema in `packages/frontend/core/src/modules/editor-settting/schema.ts`

e.g.

```ts
const BSEditorSettingSchema = z.object({
  connector: z.object({
    stroke: z
      .union([
        z.string(),
        z.object({
          dark: z.string(),
          light: z.string(),
        }),
      ])
      .default('#000000'), // default is necessary
  }),
});
```

schema can be defined in a nested way. EditorSetting api is in flat way:

editorSetting api:

```ts
editorSetting.settings$ === {
  'connector.stroke': '#000000'
}
editorSetting.set('connector.stroke', '#000')
```

and use `expandFlattenObject` function can restore the flattened structure to a nested structure. nested structure is required by blocksuite

```ts
editorSetting.settings$.map(expandFlattenObject) === {
  connector: {
    stroke: '#000000'
  }
}
```

packages/frontend/core/src/utils/__tests__/unflatten-object.spec.ts

@@ -0,0 +1,19 @@
+import { expect, test } from 'vitest';
+
+import { unflattenObject } from '../unflatten-object';
+
+test('unflattenObject', () => {
+  const ob = {
+    'a.b.c': 1,
+    d: 2,
+  };
+  const result = unflattenObject(ob);
+  expect(result).toEqual({
+    a: {
+      b: {
+        c: 1,
+      },
+    },
+    d: 2,
+  });
+});

packages/frontend/core/src/utils/index.ts

@@ -5,3 +5,4 @@ export * from './fractional-indexing';
 export * from './popup';
 export * from './string2color';
 export * from './toast';
+export * from './unflatten-object';

packages/frontend/core/src/utils/unflatten-object.ts

@@ -0,0 +1,22 @@
+export function unflattenObject(ob: any) {
+  const result: any = {};
+
+  for (const key in ob) {
+    if (!Object.prototype.hasOwnProperty.call(ob, key)) continue;
+
+    const keys = key.split('.');
+    let current = result;
+
+    for (let i = 0; i < keys.length; i++) {
+      const k = keys[i];
+      if (i === keys.length - 1) {
+        current[k] = ob[key];
+      } else {
+        current[k] = current[k] || {};
+        current = current[k];
+      }
+    }
+  }
+
+  return result;
+}