refactor(core): [CORE-20] type entry and converge initialization

packages/artplayer/src/player/attrMix.ts

@@ -0,0 +1,24 @@
+import { def } from '../utils'
+
+export interface AttributeMethods {
+  attr: {
+    (key: PropertyKey): unknown
+    (key: PropertyKey, value: unknown): unknown
+  }
+}
+
+export default function attrMix(art: { template: { $video: object } }): void {
+  const {
+    template: { $video },
+  } = art
+
+  def(art, 'attr', {
+    value(key: PropertyKey, value?: unknown): unknown {
+      // attr intentionally exposes arbitrary native/proxy properties, including symbols.
+      const target = $video as Record<PropertyKey, unknown>
+      if (value === undefined)
+        return target[key]
+      target[key] = value
+    },
+  })
+}